Diels-Alder Cycloaddition: Fawcettimine (Williams), Apiosporic Acid (Helmchen), Marginatone (Abad- Somovilla), Okilactomycin (Hoye), Vinigrol (Barriault), Plakotenin (Bihlmeier/Klopper)

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Natural Product ◽  
Diels Alder ◽  
State University ◽  
University Of Minnesota ◽  
Enantiomerically Pure ◽  
Colorado State University ◽  
Institute Of Technology ◽  
La Jolla ◽  
The University ◽  
Stereogenic Center

Highly substituted dienes and dienophiles are often reluctant participants in intermolecular Diels-Alder cycloaddition. Nevertheless, Robert M. Williams of Colorado State University, in the course of a synthesis of fawcettimine 4, was able (J. Org. Chem. 2012, 77, 4801) to prepare 3 by combining the enone 1 with the diene 2. Günter Helmchen of the Universität Heidelberg set (J. Org. Chem. 2012, 77, 4491) the single stereogenic center of 5 by Ir-catalyzed allylic alkylation. The Lewis acid that promoted the cycloaddition also conveniently removed the trityl protecting group, leading to 6, that was saponified to apiosporic acid 7. Antonio Abad-Somovilla of the Universidad de Valencia prepared (J. Org. Chem. 2012, 77, 5664) the triene 8 in enantiomerically pure form from carvone. Despite the additional substitution on the diene, cycloaddition proceeded smoothly to give 9, which was carried on to marginatone 10. One could envision that okilactomycin 13 could be formed by an intramolecular Diels-Alder cycloaddition. Thomas R. Hoye of the University of Minnesota observed (Org. Lett. 2012, 14, 828) that the tetraene tetronic acid corresponding to 11 was inert, but that the methyl ether 11 cyclized smoothly to 12. Demethylation then gave the natural product The complex polycyclic structure of vinigrol 16 challenged organic synthesis chemists for many years, until a route was established by Phil Baran of Scripps/La Jolla (Highlights September 6, 2010). Louis Barriault cyclized (Angew. Chem. Int. Ed. 2012, 51, 2111) 14 to 15 en route to a late intermediate in the Baran synthesis It had been hypothesized that the natural product plakotenin 19 was formed naturally from a tetraene corresponding to 17. The tetraene 17 was prepared and the cyclization was successful, “confirming” both the structure of the natural product and the biosynthetic hypothesis. Angela Bihlmeier and Wim Klopper of the Karlsruhe Institute of Technology calculated (J. Am. Chem. Soc. 2012, 134, 2154) the relative energies of the four competing transition states for the cyclization, leading to a correction of the structure of 18, and so of the natural product 19.

Enantioselective Assembly of Oxygenated Stereogenic Centers

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Catalyst Loading ◽  
Enantioselective Hydrolysis ◽  
State University ◽  
Stable Free Radical ◽  
Enantiomerically Pure ◽  
Institute Of Technology ◽  
North Dakota State University ◽  
The University ◽  
Low Catalyst Loading ◽  
Stereogenic Center

Reaction with an enantiomerically-pure epoxide is an efficient way to construct a molecule incorporating an enantiomerically-pure oxygenated stereogenic center. The Jacobsen hydrolytic resolution has made such enantiomerically-pure epoxides readily available from the corresponding racemates. Christopher Jones and Marcus Weck of the Georgia Institute of Technology have now (J. Am. Chem. Soc. 2007, 129, 1105) developed an oligomeric salen complex that effects the enantioselective hydrolysis at remarkably low catalyst loading. Any such approach depends on monitoring the progress of the hydrolysis, usually by chiral GC or HPLC. In a complementary approach, we (J. Org. Chem. 2007, 72, 431) have found that on exposure to NBS and the inexpensive mandelic acid 2, a terminal alkene such as 1 was converted into the two bromomandelates 3 and 4. These were readily separated by column chromatography. Individually, 3 and 4 can each be carried on the same enantiomer of the epoxide 5. As 3 and 4 are directly enantiomerically pure, epoxide 5 of high ee can be prepared reliably without intermediate monitoring by chiral GC or HPLC. Another way to incorporate an enantiomerically-pure oxygenated stereogenic center into a molecule is the enantioface-selective addition of hydride to a ketone such as 6. Alain Burgos and his team at PPG-SIPSY in France have described (Tetrahedron Lett. 2007, 48, 2123) a NaBH4 -based protocol for taking the Itsuno-Corey reduction to industrial scale. In the past, aldehydes have been efficiently α-oxygenated using two-electron chemistry. Mukund P. Sibi of North Dakota State University has recently (J. Am. Chem. Soc. 2007, 129, 4124) described a novel one-electron alternative. The organocatalyst 10 formed an imine with the aldehyde. One-electron oxidation led to an α-radical, which was trapped by the stable free radical TEMPO to give, after hydrolysis, the α-oxygenated aldehyde 11. High ee oxygenated secondary centers can also be prepared by homologation of aldehydes. Optimization of the enantioselective addition of the inexpensive acetylene surrogate 13 was recently reported (Chem. Commun. 2007, 948) by Masakatsu Shibasaki of the University of Tokyo. Note that the free alcohol of 13 does not need to be protected.

Stereocontrolled C-O Ring Construction: The Fuwa/Sasaki Synthesis of Attenol A

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Gold Catalysis ◽  
Membered Ring ◽  
Allylic Alcohol ◽  
State University ◽  
Prins Cyclization ◽  
University Of Florida ◽  
University Of Pittsburgh ◽  
Colorado State University ◽  
Institute Of Technology ◽  
The University

Since five-membered ring ethers often do not show good selectivity on equilibration, single diastereomers are best formed under kinetic control. Aaron Aponick of the University of Florida demonstrated (Organic Lett. 2008, 10, 669) that under gold catalysis, the allylic alcohol 1 cyclized to 2 with remarkable diastereocontrol. Six-membered rings also formed with high cis stereocontrol. Ian Cumpstey of Stockholm University showed (Chem. Commun. 2008, 1246) that with protic acid, allylic acetates such as 3 cyclized with clean inversion at the allylic center, and concomitant debenzylation. J. Stephen Clark of the University of Glasgow found (J. Org. Chem. 2008, 73, 1040) that Rh catalyzed cyclization of 5 proceeded with high selectivity for insertion into Ha, leading to the alcohol 6. Saumen Hajra of the Indian Institute of Technology, Kharagpur took advantage (J. Org. Chem. 2008, 73, 3935) of the reactivity of the aldehyde of 7, effecting selective addition of 7 to 8, to deliver, after reduction, the lactone 9. Tomislav Rovis of Colorado State University observed (J. Org. Chem. 2008, 73, 612) that 10 could be cyclized selectively to either 11 or 12. Nadège Lubin-Germain, Jacques Uziel and Jacques Augé of the University of Cergy- Pontoise devised (Organic Lett. 2008, 10, 725) conditions for the indium-mediated coupling of glycosyl fluorides such as 13 with iodoalkynes such as 14 to give the axial C-glycoside 15. Katsukiyo Miura and Akira Hosomi of the University of Tsukuba employed (Chemistry Lett. 2008, 37, 270) Pt catalysis to effect in situ equilibration of the alkene 16 to the more stable regioisomer. Subsequent condensation with the aldehyde 17 led via Prins cyclization to the ether 18. Paul E. Floreancig of the University of Pittsburgh showed (Angew. Chem. Int. Ed. 2008, 47, 4184) that Prins cyclization could be also be initiated by oxidation of the benzyl ether 19 to the corresponding carbocation. Chan-Mo Yu of Sungkyunkwan University developed (Organic Lett. 2008, 10, 265) a stereocontrolled route to seven-membered ring ethers, by Pd-mediated stannylation of allenes such as 21, followed by condensation with an aldehyde.

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.

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.

Alkaloid Synthesis: ( S )-Nicotine (Helmchen), (+)-CP-99,994 (Shi),(-)-Adaline (Yu), (-)-Securinine (Bayó n/Figueredo), Alkaloid 223A (Aubé ), (-)-Huperzine A (Fukuyama) 110

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Huperzine A ◽  
State University ◽  
Pd Catalysts ◽  
Enantiomerically Pure ◽  
Colorado State University ◽  
Alkaloid Synthesis ◽  
Substance P Receptor ◽  
Intramolecular Condensation ◽  
The University ◽  
Work Up

The recent development of practical methods for the asymmetric preparation of amines has enabled creative approaches to alkaloid construction. Günter Helmchen of the Ruprecht-Karls-Universit ät Heidelberg developed (Synlett 2009, 1413) an iridium catalyst that mediated the enantioselective amination of the allylic carbonate 1 to give 2. Hydroformylation followed by reduction then completed the synthesis of ( S )-nicotine 3. Yian Shi of Colorado State University devised (J. Org. Chem. 2009, 74, 7577) a Pd catalyst for the enantioselective oxidative diamination of terminal alkenes such as 4. The product 6 was readily carried on to (+)-CP-99,994, a potent and selective nonpeptide substance P receptor antagonist. Chan-Mo Yu of Sungkyunkwan University prepared (Synlett 2009, 1498) the alcohol corresponding to the azide 8 by BINOL-catalyzed addition of an allyl stannane to the corresponding aldehyde. Reduction of the azide and subsequent intramolecular condensation with the ketone gave an imine, which was cyclized with Bu3SnF to 9. Oxidative cleavage then delivered (-)-adaline 10. Barry M. Trost of Stanford University developed a family of Pd catalysts for the enantioselective coupling of racemic butadiene monoepoxide 12 with a range of nucleophiles. Pau Bayón and Marta Figueredo of the Universitat Autónoma de Barcelona extended (J. Org. Chem. 2009, 74, 6199) that range to include glutarimide 11 and succinimide. The adduct 13 provided the enantiomerically pure core for a total synthesis of (-)-securinine 14, and others of the Securinega alkaloids. Jeffrey Aubé of the University of Kansas prepared (Organic Lett. 2009, 11, 4140) the enantiomerically enriched ketone 15 by the enantioselective hydroboration of norbornadiene, followed by oxidation and alkylation. Intramolecular Schmidt cyclization following the protocol he had developed converted 15 into 16. He then took advantage of the still substantial ring strain of the expanded norbornene to drive ring-opening metathesis, giving, after hydrogenation, the lactam 17. He was able to selectively convert 17 into either 18 or the diastereomer in which the ethyl groups are cis one to another by varying the acid used in the final reductive work-up.

Enantioselective Construction of Arrays of Stereogenic Centers

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Claisen Rearrangement ◽  
Cinchona Alkaloid ◽  
State University ◽  
Henry Reaction ◽  
University Of Pittsburgh ◽  
Colorado State University ◽  
Boston University ◽  
Complementary Approach ◽  
La Jolla ◽  
The University

An impressive array of new catalysts for enantioselective homologation have been reported. Carlos F. Barbas III of Scripps/La Jolla has found (Angew. Chem. Int. Ed. 2007, 46, 5572 ) that the commercial amino acid 3 mediated the addition of dihydroxyacetone 2 to an aldehyde such as 1 to give the triol 4 with high enantio- and diastereocontrol. Takashi Ooi of Nagoya University has devised (J. Am. Chem. Soc. 2007, 129, 12392) the catalyst 6 for the anti addition (Henry reaction) of nitro alkanes such as 5 to aldehydes. Takayoshi Arai of Chiba University has developed (Organic Lett. 2007, 9, 3595) a complementary catalyst (not shown) that mediated syn addition. Jonathan A. Ellman of the University of California, Berkeley has uncovered (J. Am. Chem. Soc. 2007, 129, 15110) the catalyst 10 for the aza-Henry reaction. Yian Shi of Colorado State University has found (J. Am. Chem. Soc. 2007, 129, 11688) ligands for Pd that direct the absolute sense of the addition of 13 to dienes such as 12. Bernhard Breit of Albert-Ludwigs-Universität, Freiburg has devised conditions (Adv. Synth. Cat. 2007, 349, 1891) for the Rh-catalyzed hydroformylation of α-olefins such as 15, and same-pot proline-catalyzed condensation of the linear aldehyde so produced with a branched aldehyde such as 17 to give, after reductive workup, the branched diol 18. Scott G. Nelson of the University of Pittsburgh has established (J. Am. Chem. Soc. 2007, 129, 11690) conditions, using Cinchona alkaloid derived catalysts, for the condensation of the imine surrogate 19 with the ketene precursor 20, to give the Mannich product 21. Scott E. Schaus of Boston University has developed (J. Am. Chem. Soc. 2007, 129, 15398) a complementary approach, based on catalyzed addition of isolated allyl borinates such as 23 to the activated imine 22. Kálmán J. Szabó of Stockholm University has found (J. Am. Chem. Soc. 2007, 129, 13723) that substituted allyl borinates can be prepared and reacted in situ. Martin Hiersemann of the Universität Dortmund has reported (Organic Lett. 2007, 9, 4979) the remarkable Cu*-catalyzed Claisen rearrangement of the prochiral 24, leading to 25 and thus to the versatile intermediate 27.

Construction of Stereochemical Arrays

2015 ◽  
Author(s):  
Tristan H. Lambert
Keyword(s):  
Kinetic Resolution ◽  
Alder Reaction ◽  
State University ◽  
Rhodium Catalysis ◽  
Colorado State University ◽  
Allyl Sulfide ◽  
Institute Of Technology ◽  
Quaternary Stereocenters ◽  
The University ◽  
Technological University

The unprecedented enantioselective 1,8-addition of azlactone 1 to acylpyrrole 2 catalyzed by triaminophosphorane 3 was reported (J. Am. Chem. Soc. 2012, 134, 19370) by Takashi Ooi at Nagoya University. Tomislav Rovis at Colorado State University developed (Angew. Chem. Int. Ed. 2012, 51, 12330) the asymmetric oxidative hetero-Diels-Alder reaction of propionaldehyde (5) and ketone 6 to produce lactone 8, catalyzed by NHC catalyst 7 in the presence of phenazine. A related NHC catalyst 11 was utilized (Angew. Chem. Int. Ed. 2012, 51, 8276) by Xue-Wei Liu at Nanyang Technological University for the homoenolate addition of enal 9 to nitrodiene 10 to furnish 12 with high ee. The vinylogous conjugate addition of butenolide 13 to 15 to produce 16 with exquisite stereoselectivity was accomplished (Angew. Chem. Int. Ed. 2012, 51, 10069) by Kuo-Wei Huang at KAUST, Choon-Hong Tan at Henan University and Nanyang Technological University, and Zhiyong Jiang at Henan University. The enantioselective production of lactone 18 was achieved (J. Am. Chem. Soc. 2012, 134, 20197) by Jeffrey S. Johnson at the University of North Carolina at Chapel Hill by dynamic kinetic resolution (DKR) of α-keto ester 17. A related DKR strategy was employed (Org. Lett. 2012, 14, 6334) by Brinton Seashore-Ludlow at the KTH Royal Institute of Technology and Peter Somfai at Lund University in Sweden and the University of Tartu in Estonia for hydrogenation of α-amino-β-ketoester 19 to furnish aminoalcohol 21 with high Shigeki Matsunaga and Motomu Kanai at the University of Tokyo developed (Angew. Chem. Int. Ed. 2012, 51, 10275) a unique strategy for the selective production of the cross-aldol adduct 24 by in situ generation of an aldehyde enolate from allyloxyborane 23 under rhodium catalysis. The highly diastereoselective construction of adduct 26 bearing two adjacent quaternary stereocenters by ketone allylation with allyl sulfide 25 was reported (Angew. Chem. Int. Ed. 2012, 51, 7263) by Takeshi Takeda at the Tokyo University of Agriculture and Technology. Wen-Hao Hu at East China Normal University reported (Nature Chem. 2012, 4, 733) the enantioselective three-component coupling of diazoester 27, N-benzylindole (28), and imine 29 to furnish 31 under the action of Rh2(OAc)4 and phosphoric acid 30.

Substituted Benzenes: The Piers/Lau Synthesis of Hamigeran B

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
New York ◽  
Indian Institute ◽  
Ni Catalyst ◽  
State University ◽  
Vicarious Nucleophilic Substitution ◽  
City College ◽  
Institute Of Technology ◽  
La Jolla ◽  
University Of Bristol ◽  
The University

Govindasamy Sekar of the Indian Institute of Technology, Madras, developed ( Chem. Commun. 2011, 47, 5076) an environmentally friendly procedure for the amination of 1 to 2. Jens-Uwe Peters of Hoffmann-La Roche, Basel, showed (Tetrahedron Lett. 2011, 52, 749) that the Udenfriend protocol could be used to convert drugs such as 3 to their hydroxylated metabolites. Suman L. Jain and Anil K. Sinha of the Indian Institute of Petroleum reported (Chem. Commun. 2011, 47, 1610) complementary conditions for arene hydroxylation. Dimethyl aniline has been used, inter alia, as a nucleophile in enantioselective MacMillan conjugate addition. Zhong-Xia Wang of USTC established (Angew. Chem. Int. Ed. 2011, 50, 4901) that the quaternized salt 5 could participate in Negishi coupling. Mark R. Biscoe of the City College of New York discovered (Org. Lett. 2011, 13, 1218) that with a Ni catalyst, the secondary organozinc 9 will couple without rearrangement. Igor V. Alabugin of Florida State University devised (J. Org. Chem. 2011, 76, 1521) a radical-based protocol for replacing a phenolic OH with alkyl, to give 12. Petr Beier of the Academy of Sciences of the Czech Republic used (J. Org. Chem. 2011, 76, 4781) vicarious nucleophilic substitution followed by alkylation to convert 13 to 15. Robin B. Bedford of the University of Bristol developed (Angew. Chem. Int. Ed. 2011, 50, 5524) a Pd-catalyzed procedure for the ortho bromination of an anilide 16. Jin-Quan Yu of Scripps/La Jolla took advantage (J. Am. Chem. Soc. 2011, 133, 7652) of the energetic N-O bond of 19 to drive the functionalization of 18 to 20. Lei Liu of Tsinghua University devised (Org. Lett. 2011, 13, 3235) a Rh-mediated oxidative ortho coupling of the carbamate 21 with 22. Kohtaro Kirimura of Waseda University inserted (Chem. Lett. 2011, 40 , 206) the DNA for a novel Trichosporon decarboxylase into Escherichia coli and found that the resulting fermentation efficiently converted 24 into 25. The alternative Kolbe-Schmitt reaction requires high temperature and pressure. Sometimes, usually with more highly substituted benzene rings, creating the ring is worthwhile.

Diels–Alder Cycloaddition: Nicolaioidesin B (Coster), Lycorine (Cho), Bucidirasin A (Nakada), Maoecrystal V (Thomson), Kuwanon J (Wulff/Lei), Vinigrol (Kaliappan)

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Diels Alder ◽  
Michigan State University ◽  
State University ◽  
Ring Closing Metathesis ◽  
Enantiomerically Pure ◽  
Weinreb Amide ◽  
Maoecrystal V ◽  
Northwestern University ◽  
Peking University ◽  
Institute Of Technology

β-Ocimene 2 is an inexpensive Diels–Alder diene. En route to nicolaioidesin B 4, Mark J. Coster of Griffith University showed (Tetrahedron Lett. 2014, 55, 6864) that the Weinreb amide 1 added to the E isomer of 2 with high selectivity, to give 3. The alkaloid lycorine 8 is found throughout the Amaryllidaceae. Cheon-Gyu Cho of Hanyang University developed (Org. Lett. 2014, 16, 5718) a succinct route to 8 based on the use of the boryl styrene 5 as a Diels–Alder dienophile. Masahisa Nakada of Waseda University (Org. Lett. 2014, 16, 4734) prepared the enantiomerically-pure enone 9 by way of a baker’s yeast reduction of a prochiral dik­etone. Diels–Alder addition to 10 led to 11, that was carried on to bucidirasin A 12. Regan J. Thomson of Northwestern University prepared (J. Am. Chem. Soc. 2014, 136, 17750) the triene 13 by asymmetric epoxidation of a prochiral enone. Diels–Alder addition of the very reactive nitroethylene to give 14 completed the carbon skel­eton of maoecrystal V 15. William D. Wulff of Michigan State University and Xiaoguang Lei of Peking University optimized (Angew. Chem. Int. Ed. 2014, 53, 9257) the organocatalyzed Diels–Alder cycloaddition of 17 to the diene 16. Deprotection then completed the synthesis of the prenylflavonoid kuwanon J 18. In 2012, Barriault described (OHL 20121224) the conversion of 20 to the com­plex diterpene vinigrol 21. Krishna P. Paliappan of the Indian Institute of Technology Bombay showed (Org. Lett. 2014, 16, 5540) that the triene precursor to 20 could be prepared by ring-closing metathesis of 19. In the absence of ethylene, a different product was formed.

Heteroaromatic Construction: The Sperry Synthesis of (+)-Terreusinone

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Pt Catalyst ◽  
State University ◽  
Keto Ester ◽  
North Carolina State University ◽  
Colorado State University ◽  
Rh Catalyst ◽  
La Jolla ◽  
The University ◽  
Technological University ◽  
Convergent Assembly

Akio Saito and Yuji Hanzawa of Showa Pharmaceutical University found (Tetrahedron Lett. 2011, 52, 4658) that an alkynyl keto ester 1 could be oxidatively cyclized to the furan 2. Eric M. Ferreira of Colorado State University showed (Org. Lett. 2011, 13, 5924) that depending on the conditions, a Pt catalyst could cyclize 3 to either 4 or 5. Shunsuke Chiba of Nanyang Technological University used (J. Am. Chem. Soc. 2011, 133, 13942) Cu catalysis for the oxidation of 6 to the pyrrole 7. Vladimir Gevorgyan of the University of Illinois at Chicago devised (Org. Lett. 2011, 13, 3746) a convergent assembly of the pyrrole 10 from the alkyne 8 and the alkyne 9. Dale L. Boger of Scripps La Jolla extended (J. Am. Chem. Soc. 2011, 133, 12285) the scope of the Diels-Alder addition of the triazine 11 to an alkyne 12 to give the pyridine 13. Tomislav Rovis, also of Colorado State University, used (Chem. Commun. 2011, 47, 11846) a Rh catalyst to add an alkyne 15 to the oxime 14 to give the pyridine 16. Sensuke Ogoshi of Osaka University, under Ni catalysis, added (J. Am. Chem. Soc. 2011, 133, 18018) a nitrile 18 to the diene 17 to give the pyridine 19. Alexander Deiters of North Carolina State University showed (Org. Lett. 2011, 13, 4352) that the complex tethered diyne 20 combined with 21 with high regiocontrol to give 22. Yong-Min Liang of Lanzhou University prepared (J. Org. Chem. 2011, 76, 8329) the indole 24 by cyclizing the alkyne 23. Xiuxiang Qi and Kang Zhao of Tianjin University found (J. Org. Chem. 2011, 76, 8690) that the enamine 25 could be oxidatively cyclized to the indole 26. Kazuhiro Yoshida and Akira Yanagisawa of Chiba University established (Org. Lett. 2011, 13, 4762) that ring-closing metathesis converted the keto ester 27 to the indole 28. Alessandro Palmieri and Roberto Ballini of the Università di Camerino observed (Adv. Synth. Catal. 2011, 353, 1425) that the pyrrole 30 spontaneously added to the nitro acrylate 29 to give an adduct that cyclized to 31 on exposure to acid.

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