Total Synthesis of C–O Natural Products

2017 ◽  
Author(s):  
Tristan H. Lambert
Keyword(s):  
Total Synthesis ◽  
Claisen Rearrangement ◽  
Innovative Strategy ◽  
University Of Wisconsin ◽  
Enyne Cyclization ◽  
Free Hydroxyl ◽  
Tokyo Institute ◽  
Institute Of Technology ◽  
Oxidopyrylium Cycloaddition ◽  
The University

Weiping Tang at the University of Wisconsin, Madison reported (J. Am. Chem. Soc. 2013, 135, 12434) the total synthesis of the tropone-containing norditerpenes hain­anolidol 6 and harringtonolide 7 by making use of a strategic [5+2] oxidopyrylium cycloaddition. First, the known ketone 1 was converted through a number of steps to cycloaddition precursor 2. Treatment with DBU then effected the key cycloaddition to furnish the complex polycyclic compound 3. Additional manipulations revealed struc­ture 4 with the lactone ring in place. The tropone ring of the natural structures was con­structed by reaction of the cycloheptadiene moiety of 4 with singlet oxygen followed by Kornblum- DeLaMare rearrangement with DBU to afford ketone 5. Double elimination using TsOH then produced hainanolidol 6. The free hydroxyl of 6 was engaged in a C–H-functionalizing cyclization using Pd(OAc)₄ to yield harringtonolide 7 as well. Hanfeng Ding at Zhejiang University developed (Angew. Chem. Int. Ed. 2013, 52, 13256) a concise route to indoxamycin F 12 (as well as the related indoxamy­cins A and C). The complex intermediate 9 was accessed in only four steps from the bicyclic ketone 8, which in turn was prepared by a route involving an Ireland–Claisen rearrangement and a reductive 1,6-enyne cyclization (not shown). An impressive oxa-conjugate addition/methylenation reaction to produce 11 was accomplished by treat­ment of 9 with Grignard 10 followed by Eschenmoser’s salt. Some final decorative work then led to indoxamycin F 12. The strained polycyclophane natural product cavicularin 18 was synthesized in enantioenriched form by an innovative strategy reported (Angew. Chem. Int. Ed. 2013, 52, 10472) by Keisuke Suzuki at the Tokyo Institute of Technology.

Other Methods for Carbocyclic Construction: The Porco Synthesis of (-)-Hyperibone K

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Oxidative Cyclization ◽  
Florida State University ◽  
State University ◽  
Colorado State University ◽  
Intramolecular Alkylation ◽  
University Of Wisconsin ◽  
Tokyo Institute ◽  
Institute Of Technology ◽  
University Of Bristol ◽  
The University

Varinder K. Aggarwal of the University of Bristol described (Angew. Chem. Int. Ed. 2010, 49, 6673) the conversion of the Sharpless-derived epoxide 1 into the cyclopropane 2. Christopher D. Bray of Queen Mary University of London established (Chem. Commun. 2010, 46, 5867) that the related conversion of 3 to 5 proceeded with high diastereocontrol. Javier Read de Alaniz of the University of California, Santa Barbara, extended (Angew. Chem. Int. Ed. 2010, 49, 9484) the Piancatelli rearrangement of a furyl carbinol 6 to allow inclusion of an amine 7, to give 8. Issa Yavari of Tarbiat Modares University described (Synlett 2010, 2293) the dimerization of 9 with an amine to give 10. Jeremy E. Wulff of the University of Victoria condensed (J. Org. Chem. 2010, 75, 6312) the dienone 11 with the commercial butadiene sulfone 12 to give the highly substituted cyclopentane 13. Robert M. Williams of Colorado State University showed (Tetrahedron Lett. 2010, 51, 6557) that the condensation of 14 with formaldehyde delivered the cyclopentanone 15 with high diastereocontrol. D. Srinivasa Reddy of Advinus Therapeutics devised (Tetrahedron Lett. 2010, 51, 5291) conditions for the tandem conjugate addition/intramolecular alkylation conversion of 16 to 17. Marie E. Krafft of Florida State University reported (Synlett 2010, 2583) a related intramolecular alkylation protocol. Takao Ikariya of the Tokyo Institute of Technology effected (J. Am. Chem. Soc. 2010, 132, 11414) the enantioselective Ru-mediated hydrogenation of bicyclic imides such as 18. This transformation worked equally well for three-, four-, five-, six-, and seven-membered rings. Stefan France of the Georgia Institute of Technology developed (Org. Lett. 2010, 12, 5684) a catalytic protocol for the homo-Nazarov rearrangement of the doubly activated cyclopropane 20 to the cyclohexanone 21. Richard P. Hsung of the University of Wisconsin effected (Org. Lett. 2010, 12, 5768) the highly diastereoselective rearrangement of the triene 22 to the cyclohexadiene 23. Strategies for polycyclic construction are also important. Sylvain Canesi of the Université de Québec devised (Org. Lett. 2010, 12, 4368) the oxidative cyclization of 24 to 25.

Stereocontrolled C-N Ring Construction: The Takayama Synthesis of Lycoposerramine-C

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Biological Activity ◽  
Total Synthesis ◽  
Gold Catalyst ◽  
Allylic Alcohol ◽  
Tetramic Acids ◽  
Tokyo Institute ◽  
Chiral Bronsted Acid ◽  
Institute Of Technology ◽  
The University ◽  
Technological University

Hideki Yorimitsu and Koichiro Ochima of Kyoto University extended (Angew. Chem. Int. Ed. 2009, 48, 7224) Pd-catalyzed intramolecular carboamidation to the construction of aziridines such as 3. Hamdullah Kilic of Ataturk University showed (J. Org. Chem. 2009, 74, 9452) that aziridination of an allylic alcohol 4 could proceed with substantial diastereocontrol. Makoto Oba of Tokai University established (Tetrahedron Lett. 2009, 50, 5053) a route from a serine derivative 6 to the pyroglutamate 8 and developed a protocol for the conversion of 8 to 9. David Tanner of the Technical University of Denmark found (J. Org. Chem. 2009, 74, 5032) that tetramic acids such as 8 could also be efficiently α-arylated. Koichi Mikami of the Tokyo Institute of Technology devised (Angew. Chem. Int. Ed. 2009, 48, 6073) a gold catalyst for the enantioselective cyclization of 12 to 13. Hiroaki Sasai of Osaka University effected (J. Org. Chem. 2009, 74, 9274) double intramolecular amination, converting 14 into 15 in high ee. Kyungsoo Oh of IUPUI Indianapolis observed (Angew. Chem. Int. Ed. 2009, 48, 7420) that using the same ligand, Cu catalysis gave one enantiomer of 18 and Ag catalysis gave the opposite enantiomer. Liu-Zhu Gong of the University of Science and Technology, Hefei, devised (Organic Lett. 2009, 11, 4946) a chiral Brønsted acid that mediated the enantioselective condensation of 19, 20, and 21 to give 22. Roderick W. Bates of Nanyang Technological University found (Organic Lett. 2009, 11, 3706) that a gold catalyst mediated the cyclization of 23 to 24 with high diastereocontrol. Qi-Lin Zhou of Nankai University effected (Organic Lett. 2009, 11, 4994) the enantioselective reduction of racemic 25 under epimerizing conditions, leading to 26 with high stereocontrol. Adriaan J. Minnaard and Ben L. Feringa of the University of Groningen established (Angew. Chem. Int. Ed. 2009, 48, 9339) conditions for the enantioselective addition of a diakyl zinc to the activated pyridine 27, to give 28 in high ee. Hiromitsu Takayama of Chiba University isolated (Tetrahedron Lett. 2002, 43, 8307) lycoposerramine- C 34 from Lycopodium serratum. Intrigued by preliminary studies of the biological activity but lacking material, he developed (Organic Lett. 2009, 11, 5554) a total synthesis, the key step of which was the intramolecular Pauson-Khand cyclization of 32 to 33.

C–O Natural Products: (–)-Hybridalactone (Fürstner), (+)-Anthecotulide (Hodgson), (–)-Kumausallene (Tang), (±)-Communiol E (Kobayashi), (–)-Exiguolide (Scheidt), Cyanolide A (Rychnovsky)

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Max Planck ◽  
Enantiomerically Pure ◽  
University Of Oxford ◽  
University Of Wisconsin ◽  
Favorskii Rearrangement ◽  
Alternative Approach ◽  
Ether Oxygen ◽  
Institute Of Technology ◽  
The University ◽  
Complementary Strategy

Control of the absolute configuration of adjacent alkylated stereogenic centers is a classic challenge in organic synthesis. In the course of the synthesis of (–)-hybridalactone 4, Alois Fürstner of the Max-Planck-Institut Mülheim effected (J. Am. Chem. Soc. 2011, 133, 13471) catalytic enantioselective conjugate addition to the simple acceptor 1. The initial adduct, formed in 80% ee, could readily be recrystallized to high ee. In an alternative approach to high ee 2,3-dialkyl γ-lactones, David M. Hodgson of the University of Oxford cyclized (Org. Lett. 2011, 13, 5751) the alkyne 5 to an aldehyde, which was condensed with 6 to give 7. Coupling with 8 then delivered (+)-anthecotulide 9. The enantiomerically pure diol 10 is readily available from acetylacetone. Weiping Tang of the University of Wisconsin dissolved (Org. Lett. 2011, 13, 3664) the symmetry of 10 by Pd-mediated cyclocarbonylation. The conversion of the lactone 11 to (–)-kumausallene 12 was enabled by an elegant intramolecular bromoetherification. Shoji Kobayshi of the Osaka Institute of Technology developed (J. Org. Chem. 2011, 76, 7096) a powerful oxy-Favorskii rearrangement that enabled the preparation of both four-and five-membered rings with good diastereocontrol, as exemplified by the conversion of 13 to 14. With the electron-withdrawing ether oxygen adjacent to the ester carbonyl, Dibal reduction of 14 proceeded cleanly to the aldehyde. Addition of ethyl lithium followed by deprotection completed the synthesis of (±)-communiol E. En route to (–)-exiguolide 18, Karl A. Scheidt of Northwestern University showed (Angew. Chem. Int. Ed. 2011, 50, 9112) that 16 could be cyclized efficiently to 17. The cyclization may be assisted by a scaffolding effect from the dioxinone ring. Dimeric macrolides such as cyanolide A 21 are usually prepared by lactonization of the corresponding hydroxy acid. Scott D. Rychnovsky of the University of California Irvine devised (J. Am. Chem. Soc. 2011, 133, 9727) a complementary strategy, the double Sakurai dimerization of the silyl acetal 19 to 20.

Reactions of Alkenes

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Radical Addition ◽  
Aqueous Hydrogen Peroxide ◽  
Metal Centers ◽  
Pincer Complex ◽  
Northwestern University ◽  
Radical Reduction ◽  
Tokyo Institute ◽  
Institute Of Technology ◽  
University Of Bern ◽  
The University

Fung-E Hong of the National Chung Hsing University devised (Adv. Synth. Catal. 2011, 353, 1491) a protocol for the oxidative cleavage of an alkene 1 (or an alkyne) to the carboxylic acid 2. Patrick H. Dussault of the University of Nebraska found (Synthesis 2011, 3475) that Na triacetoxyborohydride reduced the methoxy hydroperoxide from the ozonolysis of 3 to the aldehyde 4. Reductive amination of 4 can be effected in the same pot with the same reagent. Philippe Renaud of the University of Bern used (J. Am. Chem. Soc. 2011, 133, 5913) air to promote the free radical reduction to 6 of the intermediate from the hydroboration of 5. Robert H. Grubbs of Caltech showed (Org. Lett. 2011, 13, 6429) that the phosphonium tetrafluoroborate 8 prepared by hydrophosphonation of 7 could be used directly in a subsequent Wittig reaction. Dominique Agustin of the Université de Toulouse epoxidized (Adv. Synth. Catal. 2011, 353, 2910) the alkene 9 to 10 without solvent other than the commercial aqueous t-butyl hydroperoxide. Justin M. Notestein of Northwestern University effected (J. Am. Chem. Soc. 2011, 133, 18684) cis dihydroxylation of 9 to 11 using 30% aqueous hydrogen peroxide. Chi-Ming Che of the University of Hong Kong devised (Chem. Commun. 2011, 47, 10963) a protocol for the anti-Markownikov oxidation of an alkene 12 to the aldehyde 13. Aziridines such as 14 are readily prepared from alkenes. Jeremy B. Morgan of the University of North Carolina Wilmington uncovered (Org. Lett. 2011, 13, 5444) a catalyst that rearranged 14 to the protected amino alcohol 15. A monosubstituted alkene 16 is particularly reactive both with free radicals and with coordinately unsaturated metal centers. A variety of transformations of monosubstituted alkenes have been reported. Nobuharu Iwasawa of the Tokyo Institute of Technology employed (J. Am. Chem. Soc. 2011, 133, 12980) a Pd pincer complex to catalyze the oxidative monoborylation of 16 to give 17. The 1,1-bis boryl derivatives could also be prepared. Professor Renaud effected (J. Am. Chem. Soc. 2011, 133, 13890) radical addition to 16 leading to the terminal azide 18.

C–O Ring-Containing Natural Products: Cyanolide A (Krische), Bisabosqual A (Parker), Iso-Eriobrucinol A (Hsung), Trichodermatide A (Hiroya), Batrachotoxin Core (Du Bois)

2017 ◽  
Author(s):  
Tristan H. Lambert
Keyword(s):  
Total Synthesis ◽  
Natural Product ◽  
Radical Cyclization ◽  
Ethyl Vinyl ◽  
University Of Texas ◽  
Iridium Catalysis ◽  
University Of Wisconsin ◽  
Bisabosqual A ◽  
The University ◽  
Very High

Michael J. Krische at the University of Texas at Austin developed (Angew. Chem. Int. Ed. 2013, 52, 4470) a total synthesis of cyanolide A 7 in only seven steps, a sequence so short it is shown here in its entirety. Diol 1 was subjected to enantioselective cat­alytic bisallylation under iridium catalysis to furnish 2 with very high levels of ste­reocontrol. Cross metathesis using ruthenium catalyst 3 first with ethyl vinyl ketone and then with ethylene resulted in the production of pyran 4. Glycosylation of 4 with phenylthioglycoside 5, stereoselective reduction of the ketone function, and oxidative cleavage of the olefin then furnished the carboxylic acid 6. Finally, dimerization of 6 with 2-methyl-6-nitrobenzoic anhydride (MBNA) yielded cyanolide A. Kathlyn A. Parker at Stony Brook University reported (J. Am. Chem. Soc. 2013, 135, 582) a tandem radical cyclization strategy for the total synthesis of bisabosqual A 11. The key substrate 9 was prepared in three steps from the diester 8. Treatment of 9 with tri-s-butylborane and TTMS in the presence of air induced the tandem 5-exo, 6-exo radical cyclization to produce the complete core 10 of the natural product as a mixture of diastereomers, which could be equilibrated. Some further redox maneu­vers then led to bisabosqual A. Richard P. Hsung at the University of Wisconsin, Madison disclosed (Org. Lett. 2013, 15, 3130) a very brief synthesis of iso-eriobrucinol A and related isomers using a unique cascade sequence. First, phloroglucinol 12 and citral 13 were condensed using piperidine and acetic anhydride. The product of this operation was the tetracy­clic cyclobutane 14, the result of an oxa-[3+3] annulation followed by a stepwise, cat­ionic [2+2] cycloaddition. Treatment of 14 with methyl propiolate in the presence of catalytic indium(III) chloride under microwave irradiation furnished iso-eriobrucinol A, as well as the isomeric natural product iso-eriobrucinol B. A concise approach to trichodermatide A 19 was developed (Angew. Chem. Int. Ed. 2013, 52, 3546) by Kou Hiroya at Musashino University. Aldehyde 16, which was syn­thesized from L-tartaric acid, was condensed with 1,3-cyclohexanedione in the presence of piperidine, resulting in diketone 17.

Alkenes

2017 ◽  
Author(s):  
Allison K. Griffith ◽  
Tristan H. Lambert
Keyword(s):  
State University ◽  
One Pot ◽  
Colorado State University ◽  
University Of Oxford ◽  
University Of British Columbia ◽  
University Of Wisconsin ◽  
Unsaturated Carbonyl Compound ◽  
Institute Of Technology ◽  
University Of Zurich ◽  
The University

The α-C–H functionalization of piperidine catalyzed by tantalum complex 1 to pro­duce amine 2 was developed (Org. Lett. 2013, 15, 2182) by Laurel L. Schafer at the University of British Columbia. An asymmetric diamination of diene 3 with diaziri­dine reagent 4 under palladium catalysis to furnish cyclic sulfamide 5 was developed (Org. Lett. 2013, 15, 796) by Yian Shi at Colorado State University. Enantioenriched β-fluoropiperdine 8 was prepared (Angew. Chem. Int. Ed. 2013, 52, 2469) via amino­fluorocyclization of 6 with hypervalent iodide 7, as reported by Cristina Nevado at the University of Zurich. Erick M. Carreira at ETH Zürich disclosed (J. Am. Chem. Soc. 2013, 135, 6814) a ruthenium-catalyzed hydrocarbamoylation of allylic formamide 9 to yield pyrrolidone 10. Hans-Günther Schmalz at the University of Köln disclosed (Angew. Chem. Int. Ed. 2013, 52, 1576) an asymmetric hydrocyanation of styrene 11 with Ni(cod)₂ and phosphine–phosphite ligand 12 to yield exclusively the branched cyanide 13. A simi­lar transformation of styrene 11 to the hydroxycarbonylated product 15 was catalyzed (Chem. Commun. 2013, 49, 3306) by palladium complex 14, as reported by Matthew L. Clarke at the University of St Andrews. Feng-Ling Qing at the Chinese Academy of Sciences found (Angew. Chem. Int. Ed. 2013, 52, 2198) that the hydrotrifluoromethylation of unactivated alkene 16 to 17 was catalyzed by silver nitrate. The same transformation was also reported (J. Am.Chem. Soc. 2013, 135, 2505) by Véronique Gouverneur at the University of Oxford using a ruthenium photocatalyst and the Umemoto reagent 18. Clark R. Landis at the University of Wisconsin, Madison reported (Angew. Chem. Int. Ed. 2013, 52, 1564) a one-pot asymmetric hydroformylation using 21 followed by Wittig olefination to transform alkene 19 into the γ-chiral α,β-unsaturated carbonyl compound 20. Debabrata Mati at the Indian Institute of Technology Bombay found (J. Am. Chem. Soc. 2013, 135, 3355) that alkene 22 could be nitrated stereoselectively with silver nitrite and TEMPO to form alkene 23. Damian W. Young at the Broad Institute disclosed (Org. Lett. 2013, 15, 1218) that a macrocyclic vinylsiloxane 24, which was synthesized via an E-selective ring clos­ing metathesis reaction, could be functionalized to make either E- or Z-alkenes, 25 and 26.

Carbocyclic Construction: The Deng Synthesis of (-)-Plicatic Acid

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Brefeldin A ◽  
Conjugate Addition ◽  
Oxidative Cyclization ◽  
Ring Closure ◽  
Silyl Ether ◽  
University Of Pittsburgh ◽  
University Of Wisconsin ◽  
Institute Of Technology ◽  
The University ◽  
Academy Of Sciences

Tehshik P. Yoon of the University of Wisconsin uncovered (J. Am. Chem. Soc. 2009, 131, 14604) conditions for the crossed photodimerization of acyclic enones. Minoru Isobe of Nagoya University extended (Synlett 2009, 1157) conjugate addition–intramolecular epoxide opening to substrates such as 4, leading to the cyclobutane 6 with high diastereocontrol. In the course of a total synthesis of (+)-brefeldin A, Jinsung Tae of Yonsei University established (Synlett 2009, 1303) conditions for the trans-selective cyclization of 7 to 8. Cyclization with TiCl4 gave the alternative cis diastereomer. Several methods have been put forward for the conversion of carbohydrate derivatives to carbocycles. Yeun-Mi Tsai of the National Taiwan University found (Tetrahedron Lett . 2009, 50, 3805) that acyl silanes such as 9 cyclized efficiently under free radical conditions, leading to the silyl ether 10. Tanmaya Pathak of the Indian Institute of Technology, Kharagpur, developed (Eur. J. Org. Chem. 2009, 872) the tandem conjugate addition– intramolecular alkylation conversion of 11 to 13. Slawomir Jarosz of the Polish Academy of Sciences, Warsawza, observed (Heterocycles 2009, 80, 1303) that the oxime derived from 14 cyclized to 15. The cyclization was accelerated by high pressure. Cyclohexanes can also be prepared from carbohydrates. Tony K. M. Shing of the Chinese University of Hong Kong showed (Organic. Lett. 2009, 11, 5070) that the nitrile oxide derived from 16 cyclized to 17, that he carried on to (-)-gabosine O. John K. Gallos of the Aristotle University of Thessaloniki described (Tetrahedron Lett. 2009, 50, 6916) related work. Paul E. Floreancig of the University of Pittsburgh devised (Organic. Lett. 2009, 11, 3152) conditions for the oxidative cyclization of 18 to 19. Ring closure proceeded with high equatorial selectivity. Kou Hiroya of Tohoku University found (J. Org. Chem. 2009, 74, 6623) that the single oxygenated stereogenic center of 20 directed the dissolving metal reduction–enolate trapping, leading to 21. Similarly, Susumu Kobayashi of the Tokyo University of Science showed (Synlett 2009, 1605) that the oxygenated stereogenic centers of 22 set the alkylated centers of 23. Many marine organisms are able to carry out brominative and chlorinative polyolefin cyclizations.

Synthesis and Reactions of Alkenes

2015 ◽  
Author(s):  
Tristan H. Lambert
Keyword(s):  
Stereoselective Synthesis ◽  
Rhodium Complex ◽  
University Of Wisconsin ◽  
Federal Institute ◽  
Institute Of Technology ◽  
La Jolla ◽  
University Of Bristol ◽  
The University ◽  
Academy Of Sciences ◽  
Trisubstituted Alkenes

Christine L. Willis and Varinder K. Aggarwal at the University of Bristol have developed (Angew. Chem. Int. Ed. 2012, 51, 12444) a procedure for the diastereodivergent synthesis of trisubstituted alkenes via the protodeboronation of allylic boronates, such as in the conversion of 1 to either 2 or 3. An alternative approach to the stereoselective synthesis of trisubstituted alkenes involving the reduction of the allylic C–O bond of cyclic allylic ethers (e.g., 4 to 5) was reported (Chem. Commun. 2012, 48, 7844) by Jon T. Njardarson at the University of Arizona. A novel synthesis of allylamines was developed (J. Am. Chem. Soc. 2012, 134, 20613) by Hanmin Huang at the Chinese Academy of Sciences with the Pd(II)-catalyzed vinylation of styrenes with aminals (e.g. 6 + 7 to 8). Eun Jin Cho at Hanyang University showed (J. Org. Chem. 2012, 77, 11383) that alkenes such as 9 could be trifluoromethylated with iodotrifluoromethane under visible light photoredox catalysis. David A. Nicewicz at the University of North Carolina at Chapel Hill developed (J. Am. Chem. Soc. 2012, 134, 18577) a photoredox procedure for the anti-Markovnikov hydroetherification of alkenols such as 11, using the acridinium salt 12 in the presence of phenylmalononitrile (13). A unique example of “catalysis through temporary intramolecularity” was reported (J. Am. Chem. Soc. 2012, 134, 16571) by André M. Beauchemin at the University of Ottawa with the formaldehyde-catalyzed Cope-type hydroamination of allyl amine 15 to produce the diamine 16. A free radical hydrofluorination of unactivated alkenes, including those bearing complex functionality such as 17, was developed (J. Am. Chem. Soc. 2012, 134, 13588) by Dale L. Boger at Scripps, La Jolla. Jennifer M. Schomaker at the University of Wisconsin at Madison reported (J. Am. Chem. Soc. 2012, 134, 16131) the copper-catalyzed conversion of bromostyrene 19 to 20 in what was termed an activating group recycling strategy. A rhodium complex 23 that incorporates a new chiral cyclopentadienyl ligand was developed (Science 2012, 338, 504) by Nicolai Cramer at the Swiss Federal Institute of Technology in Lausanne and was shown to promote the enantioselective merger of hydroxamic acid derivative 21 and styrene 22 to produce 24.

Reduction of Organic Functional Groups

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Functional Groups ◽  
Selective Reduction ◽  
Terminal Alkyne ◽  
Hypophosphorous Acid ◽  
Claude Bernard ◽  
Organic Functional Groups ◽  
Tokyo Institute ◽  
Institute Of Technology ◽  
Ag Catalyst ◽  
The University

Cornelis J. Elsevier of the University of Amsterdam developed (ACS Catal. 2014, 4, 1349) an improved Pd-based protocol for the hydrogenation of an alkyne 1 to the Z-alkene 2. Yongbo Zhou and Shuang-Feng Yin of Hunan University showed (Adv. Synth. Catal. 2014, 356, 765) that under Cu catalysis, hypophosphorous acid selec­tively reduced the terminal alkyne of 3 to the ene-yne 4. Hidefumi Makabe of Shinshu University found (Tetrahedron Lett. 2014, 55, 2822) that the iodoalkyne 5 was reduced to the iodoalkene 6 by diimide, conveniently generated from the arenesulfo­nyl hydrazide. Manat Pohmakotr of Mahidol University used (Eur. J. Org. Chem. 2014, 1708) P- 2 Ni to reduce the sulfoxide 7 to the alkene 8. Shinya Furakawa and Takayuki Komatsu of the Tokyo Institute of Technology devised (ACS Catal. 2014, 4, 1441) a Pd catalyst for the selective reduction of the nitro group of 9 to the aniline 10. Hiroshi Kominami of Kinki University employed (Chem. Commun. 2014, 50, 4558) a Ti- promoted Ag catalyst to deoxygenate the epoxide 11 to the alkene 12. Benjamin R. Buckley and K. G. Upul Wijayantha of Loughborough University described (Synlett 2014, 25, 197) an alternative protocol (not illustrated) for epoxide deoxygenation. Xiaohui Fan of Lanzhou Jiaotong University observed (Eur. J. Org. Chem. 2014, 498) that the reduction of 13 to 14 proceeded without cyclopropane opening, sug­gesting the reaction did not involve substantial charge separation. Michel R. Gagné of the University of North Carolina deployed (Angew. Chem. Int. Ed. 2014, 53, 1646) cat­alytic trispentafluorophenylborane to selectively reduce 15 to 16. Gojko Lalic of the University of Washington reduced (Angew. Chem. Int. Ed. 2014, 53, 752) a secondary iodide 17 to the hydrocarbon 18 under Cu catalysis. Primary bromides and triflates could also be reduced, while many other functional groups, including tosylates, were stable. Marc Lemaire of the Université Claude-Bernard Lyon 1 converted (Tetrahedron Lett. 2014, 55, 23) the nitrile 19 to the aldehyde 20 by V-catalyzed reduction followed by hydrolysis. Matthias Beller of the Universität Rostock showed (Chem. Eur. J. 2014, 20, 4227) that a nitrile 21 could be reduced to the amine 22 with very little by- product dimer.

Heteroaromatic Construction: The Jia Synthesis of (-)- cis -Clavicipitic Acid

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
Aldol Condensation ◽  
Streptomyces Coelicolor ◽  
University Of Florida ◽  
Bacterial Signaling ◽  
Shanghai Institute ◽  
Tokyo Institute ◽  
Institute Of Technology ◽  
The University ◽  
Technological University

Simultaneously, Aaran Aponick of the University of Florida (Organic Lett. 2009, 11, 4624) and Shuji Akai of the University of Shizuoka (Organic Lett. 2009, 11, 5002) reported the Au-mediate conversion of a propargylic diol such as 1 to the furan 2. Pyrroles can also be prepared using the same protocol. Jason K. Sello of Brown University developed (Organic Lett. 2009, 11, 2984) the direct aldol condensation of an acetoacetate 3 with the protected 1,3-dihydroxy acetone 4 to give 5, the methyl ester of a methylenomycin furan (MMF) bacterial-signaling molecule from Streptomyces coelicolor. Nobuharu Iwasawa of the Tokyo Institute of Technology demonstrated (Angew. Chem. Int. Ed. 2009, 48, 8318) that the imine 6 was sufficiently nucleophilic to react with the Rh vinylidene derived from the alkyne 7, leading to the pyrrole 8. Min Shi of the Shanghai Institute of Organic Chemistry extended (J. Org. Chem. 2009, 74, 5983) the reactivity of methylene cyclopropanes to the condensation of the aldehyde 9 with an acyl hydrazide, to give the pyrrole 11. Xue-Long Hou, also of the Shanghai Institute of Organic Chemistry, described (Tetrahedron Lett. 2009, 50, 6944) the Au-mediated reorganization of the alkynyl aziridine 12 to the pyrrole 13. Masahiro Yoshida of the University of Tokushima carried out (Tetrahedron Lett. 2009, 50, 6268) a similar rearrangement under oxidative conditions, giving the iodinated pyrrole 15. André M. Beauchemin of the University of Ottawa showed (Angew. Chem. Int. Ed. 2009, 48, 8325) that under acid catalysis, the oxime 16 cyclized to the pyridine 17. Shunsuke Chiba of Nanyang Technological University developed (J. Am. Chem. Soc. 2009, 131, 12570) the Mn(III)-mediated fusion of a cyclopropanol 18 with an alkenyl azide 19 to deliver the pyridine 20. Kazuaki Shimada of Iwate University found (Tetrahedron Lett. 2009, 50, 6651) that an isotellurazole such as 21, easily prepared from the corresponding alkyne, condensed with another alkyne 22, delivering the pyridine 23 with high regiocontrol. Christopher J. Moody of the University of Nottingham devised (Organic Lett. 2009, 11, 3686) a new route to the 1,2,4-triazine 24 from an α-diazoacetoacetate. He carried 24 on to the pyridine 26 by condensation with norbornadiene 25.

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