Substituted Benzenes: The Alvarez- Manzaneda Synthesis of (–)-Akaol A

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Bond Formation ◽  
University Of Michigan ◽  
Aromatic Substitution ◽  
Substituted Benzenes ◽  
University Of Oklahoma ◽  
Meta Position ◽  
Substitution Chemistry ◽  
La Jolla ◽  
The University ◽  
École Polytechnique

Ramin Ghorbani-Vaghei of Bu-Ali Sina University devised (Tetrahedron Lett. 2012, 53, 2325) conditions for the bromination of an electron-deficient arene such as 1. Yonghong Gu of the University of Science and Technology of China found (Tetrahedron Lett. 2011, 52, 4324) that an electron-rich anilide 3 could be oxidized to 4. Sukbok Chang of KAIST (J. Am. Chem. Soc. 2012, 134, 2528) and Kouichi Ohe of Kyoto University (Chem. Commun. 2012, 48, 3127) devised protocols for the oxidative cyanation of 5 to 6. Phenylazocarboxylates and triazenes are stable, but have the reaction chemistry of diazonium salts. The aromatic substitution chemistry of these derivatives has not been much explored. As illustrated by the conversion of 7 to 8, reported (J. Org. Chem. 2012, 77, 1520) by Markus R. Heinrich of the Universität Erlangen-Nürnberg, the benzene ring of the phenylazocarboxylate is reactive with nucleophiles. In contrast, triazene-activated benzene rings should be particularly reactive with electrophiles, as exemplified by the transformation, below, of 20 to 21. Melanie S. Sanford of the University of Michigan observed (Org. Lett. 2012, 14, 1760) good selectivity for 12 in the Pd-catalyzed reaction of 10 with 11. Jérôme Waser of the Ecole Polytechnique Fédérale de Lausanne used (Org. Lett. 2012, 14, 744) 14 to alkynylate 13 to give 15. Sulfonyl chlorides such as 16 are readily prepared from the corresponding arene, and many are commercially available. Jiang Cheng of Wenzhou University found (Chem. Commun. 2012, 48, 449) conditions for the direct cyanation of 16 to 17. Kenneth M. Nicholas of the University of Oklahoma effected (J. Org. Chem. 2012, 77, 5600) selective ortho bromination of the carbamate 18 to give 19. Stefan Bräse of KIT observed (Angew. Chem. Int. Ed. 2012, 51, 3713) ortho trifluoromethylation of the triazene 20 to give 21. Ji-Quan Yu of Scripps/La Jolla designed (Nature 2012, 486, 518) the benzyl ether 22 to activate the arene for C–C bond formation at the meta position to give 23. Guo-Jun Deng of Xiangtan University employed (Org. Lett. 2012, 14, 1692) a borrowed hydrogen strategy to effect aromatization of 24 with nitrobenzene to give the aniline 25.

Synthesis of Substituted Benzenes: The Carter Synthesis of Siamenol

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Aryl Halides ◽  
Substituted Benzenes ◽  
Diversity Oriented Synthesis ◽  
University Of Illinois ◽  
University Of Houston ◽  
Direct Functionalization ◽  
University Of Edinburgh ◽  
Aryl Tosylates ◽  
La Jolla ◽  
The University

Tosylates are among the least expensive, but also among the least reactive toward Pd(0) oxidative addition, of aryl sulfonates. Jie Wu of Fudan University has now devised conditions (J. Org. Chem. 2007, 72, 9346) for the Pd-catalyzed coupling of aryl tosylates such as 1 with arene trifluoroborates. Kei Manabe of RIKEN has found (Organic Lett. 2007, 9, 5593) that an ortho OH activates an adjacent Cl for Pd-mediated coupling, allowing the conversion of 4 to 6 . Philippe Uriac and Pierre van de Weghe of the Université de Rennes I have developed (Organic Lett. 2007, 9, 3623) conditions for the catalytic acylation of aryl halides with alkenyl acetates such as 8. Multi-component coupling lends itself well to diversity-oriented synthesis. As illustrated by the combination of 10 with 11 and 12 to give 13 reported (Organic Lett. 2007, 9, 5589) by Michael F. Greaney of the University of Edinburgh, benzynes can do double addition with high regiocontrol. For other recent references to unsymmetrical double additions to arynes, see Angew.Chem. Int. Ed. 2007, 46, 5921; Chem. Commun. 2007, 2405; and J. Am. Chem. Soc. 2006, 128, 14042. C-H functionalization of arenes is of increasing importance. John F. Hartwig of the University of Illinois has described (Organic Lett. 2007, 9, 757; 761) improved conditions for Ir-catalyzed meta borylation, and conditions for further coupling of the initial borate 16 to give amines such as 17. Lei Liu and Qing-Xiang Guo of the University of Science and Technology, Hefei have found (Tetrahedron Lett. 2007, 48, 5449) that oxygen can be used as the stoichiometric oxidant in the Pd-catalyzed functionalization of H’s ortho to anilides. Two other research groups (J. Am. Chem. Soc. 2007, 129, 6066; Angew. Chem. Int. Ed. 2007, 46, 5554; J. Org. Chem. 2007, 72, 7720) reported advances in this area. In a close competition, Jin-Quan Yu, now at Scripps/La Jolla (J. Am. Chem. Soc. 2007, 129, 3510) and Olafs Daugulis of the University of Houston (J. Am. Chem. Soc. 2007, 129, 9879) both reported that a carboxyl group can activate an ortho H for direct functionalization.

C-H Functionalization to Form C-O, C-N, and C-C Bonds

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Vinyl Ether ◽  
Boronic Acid ◽  
Bond Formation ◽  
University Of Maryland ◽  
Tsinghua University ◽  
Statistical Mixture ◽  
Mild Conditions ◽  
Hydride Abstraction ◽  
La Jolla ◽  
The University

A classic example of C-H functionalization is the familiar NBS bromination of a benzylic site. Recent updates of this approach allow for direct alkoxylation (J. Am. Chem. Soc. 2008, 130, 7824) and net amination (Organic Lett. 2008, 10, 1863). For the amination of simple aliphatic H’s, Holger F. Bettinger of Ruhr-Universität Bochum developed (Angew. Chem. Int. Ed. 2008, 47, 4744) the boryl azide 2. The insertion with 1 proceeded to give a statistical mixture of the nitrene insertion products 3 and 4. The tethered C-H functionalization devised (J. Am. Chem. Soc. 2008, 130, 7247) by Phil S. Baran of Scripps-La Jolla is selective, as in the conversion to 5 to 6, but appears to be limited to tertiary and benzylic C-H sites. Michael P. Doyle of the University of Maryland established (J. Org. Chem. 2008, 73, 4317) an elegant protocol for the oxidation of an alkyne such as 7 to the ynone 8. Note that the oxidation did not move the alkyne. Marta Catellani of the Università di Parma reported (Adv. Synth. Cat. 2008, 350, 565) the intriguing Pd-catalyzed conversion of 9 to 10. Under mild conditions, it might likely be possible to hydrolyze the vinyl ether to reveal the phenol 11. Another way of looking at this overall transformation would be to consider the ether 10 to be a protected form of the aldehyde 12. C-H activation can also lead to C-C bond formation. Irena S. Akhrem of the Nesmeyanov Institute, Moscow, described (Tetrahedron Lett. 2008, 49, 1399) a hydride-abstraction protocol for three-component coupling of a hydrocarbon 13 , an amine 14 , and CO, leading to the homologated amide 15. Hua Fu of Tsinghua University, Beijing, showed (J. Org. Chem. 2008 , 73, 3961) that oxidation of an amine 16 led to an intermediate that could be coupled with an alkyne 17 to give the propargylic amine 18. Products 15 and 18 are the result of sp2 and sp coupling, respectively. C-H functionalization leading to sp3 -sp3 coupling is less common. Jin-Quan Yu of Scripps/La Jolla found (J. Am. Chem. Soc. 2008, 130, 7190) that activation of the N-methoxy amide 19 in the presence of the alkyl boronic acid 20 gave smooth coupling, to 21.

Functionalization and Homologation of C-H Bonds

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Crop Protection ◽  
Oxidative Cyclization ◽  
South Florida ◽  
State University ◽  
Ru Catalyst ◽  
University Of Oklahoma ◽  
Princeton University ◽  
La Jolla ◽  
The University ◽  
Technological University

Justin Du Bois of Stanford University developed (J. Am. Chem. Soc. 2010, 132, 10202) a Ru catalyst for the stereoretentive hydroxylation of 1 to 2. John T. Groves of Princeton University effected (J. Am. Chem. Soc. 2010, 132, 12847) equatorial chlorination of the test substrate 3. Kenneth M. Nicholas of the University of Oklahoma found (J. Org. Chem. 2010, 75, 7644) that I2 catalyzed the amination of 5. Thorsten Bach of the Technische Universität München established (Org. Lett. 2010, 12, 3690) that the amination of 7 proceeded with significant diastereoselectivity. Phil S. Baran of Scripps/La Jolla compiled (Synlett 2010, 1733) an overview of the development of C-H oxidation. Tethering can improve the selectivity of C-H functionalization. X. Peter Zhang of the University of South Florida devised (Angew. Chem. Int. Ed. 2010, 49, 10192) a Co catalyst for the cyclization of 9 to 10. Teck-Peng Loh of Nanyang Technological University established (Angew. Chem. Int. Ed. 2010, 49, 8417) conditions for the oxidation of 11 to 12. Jin-Quan Yu, also of Scripps/La Jolla, effected (J. Am. Chem. Soc. 2010, 132, 17378) carbonylation of methyl C-H of 13 to give 14. Sunggak Kim, now also at Nanyang Technological University, established (Synlett 2010, 1647) conditions for the free-radical homologation of 15 to 17. Gong Chen of Pennsylvania State University extended (Org. Lett. 2010, 12, 3414) his work on remote Pd-mediated activation by cyclizing 18 to 19. Many schemes have been developed in recent years for the oxidation of substrates to reactive electrophiles. Gonghua Song of the East China University of Science and Technology and Chao-Jun Li of McGill University reported (Synlett 2010, 2002) Fe nanoparticles for the oxidative coupling of 20 with 21. Zhi-Zhen Huang of Nanjing University found (Org. Lett. 2010, 12, 5214) that protonated pyrrolidine 25 was important for mediating the site-selective coupling of 24 with 23. Y. Venkateswarlu of the Indian Institute of Chemical Technology, Hyderabad, was even able (Tetrahedron Lett. 2010, 51, 4898) to effect coupling with a cyclic alkene 28. AB3217-A 32, isolated in 1992, was shown to have marked activity against two spotted spider mites. Christopher R. A. Godfrey of Syngenta Crop Protection, Münchwilen, prepared (Synlett 2010, 2721) 32 from commercial anisomycin 30a. The key step in the synthesis was the oxidative cyclization of 30b to 31.

Flow Chemistry

2015 ◽  
Author(s):  
Tristan H. Lambert
Keyword(s):  
Continuous Flow ◽  
Flow Chemistry ◽  
Ethyl Vinyl Ether ◽  
University Of Michigan ◽  
Ethyl Vinyl ◽  
Photochemical Rearrangement ◽  
Osaka Prefecture ◽  
La Jolla ◽  
University Of Bristol ◽  
The University

Timothy F. Jamison at MIT developed (Org. Lett. 2013, 15, 710) a metal-free continuous-flow hydrogenation of alkene 1 using the protected hydroxylamine reagent 2 in the presence of free hydroxylamine. The reduction of nitroindole 4 to the corresponding aniline 5 using in situ-generated iron oxide nanocrystals in continuous flow was reported (Angew. Chem. Int. Ed. 2012, 51, 10190) by C. Oliver Kappe at the University of Graz. A flow method for the MPV reduction of ketone 6 to alcohol 7 was disclosed (Org. Lett. 2013, 15, 2278) by Steven V. Ley at the University of Cambridge. Corey R.J. Stephenson, now at the University of Michigan, developed (Chem. Commun. 2013, 49, 4352) a flow deoxygenation of alcohol 8 to yield 9 using visible light photoredox catalysis. Stephen L. Buchwald at MIT demonstrated (J. Am. Chem. Soc. 2012, 134, 12466) that arylated acetaldehyde 11 could be generated from aminopyridine 10 by diazonium formation and subsequent Meerwein arylation of ethyl vinyl ether in flow. The team of Takahide Fukuyama and Ilhyong Ryu at Osaka Prefecture University showed (Org. Lett. 2013, 15, 2794) that p-iodoanisole (12) could be converted to amide 13 via low-pressure carbonylation using carbon monoxide generated from mixing formic and sulfuric acids. The continuous-flow Sonogashira coupling of alkyne 14 to produce 15 using a Pd-Cu dual reactor was developed (Org. Lett. 2013, 15, 65) by Chi-Lik Ken Lee at Singapore Polytechnic. A tandem Sonogashira/cycloisomerization procedure to convert bromopyridine 16 to aminoindolizine 18 in flow was realized (Adv. Synth. Cat. 2012, 354, 2373) by Keith James at Scripps, La Jolla. A procedure for the Pauson-Khand reaction of alkene 19 to produce the bicycle 20 in a photochemical microreactor was reported (Org. Lett. 2013, 15, 2398) by Jun-ichi Yoshida at Kyoto University. Kevin I. Booker-Milburn at the University of Bristol discovered (Angew. Chem. Int. Ed. 2013, 52, 1499) that irradiation of N-butenylpyrrole 21 in flow produced the rearranged tricycle 22. Professor Jamison described (Angew. Chem. Int. Ed. 2013, 52, 4251) a unique peptide coupling involving the photochemical rearrangement of nitrone 23 to the hindered dipeptide 24 in continuous flow.

Preparation of Substituted Benzenes: The Beaudry Synthesis of Arundamine

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
De Novo ◽  
Benzyl Bromide ◽  
Benzene Derivative ◽  
University Of Texas ◽  
Ortho Metalation ◽  
Cu Catalyst ◽  
Aryl Grignard Reagent ◽  
La Jolla ◽  
The University ◽  
École Polytechnique

Stephen G. DiMagno of the University of Nebraska developed (Chem. Eur. J. 2015, 21, 6394) a protocol for the clean monoiodination of 1 to 2. The bromomethylation (or chloromethylation, with HCl) of a benzene derivative is straightforward with formal­dehyde and HBr. Naofumi Tsukada of Shizuoka University designed (Organometallics 2015, 34, 1191) a Cu catalyst that mediated the coupling of an alkyne with the benzyl bromide so produced, effecting net propargylation of 3 with 4 to give 5. Triazenes such as 7, versatile intermediates for organic synthesis, are usually prepared by diazotization of the corresponding aniline. Kay Severin of the Ecole Polytechnique Fédérale de Lausanne established (Angew. Chem. Int. Ed. 2015, 54, 302) an alternative route from the aryl Grignard reagent 6. Ping Lu and Yanguang Wang of Zhejiang University showed (Chem. Commun. 2015, 51, 2840) that dimethylformamide could serve as the carbon source for the conversion of 8 to the nitrile 9. Junha Jeon of the University of Texas at Arlington effected (J. Org. Chem. 2015, 80, 4661; Chem. Commun. 2015, 51, 3778) the reductive ortho silylation of 10 to give 11. Vladimir Gevorgyan of the University of Illinois at Chicago found (Angew. Chem. Int. Ed. 2015, 54, 2255) that the phenol derivative 12 could be ortho carboxylated, leading to 13. Lutz Ackermann of the Georg-August-Universität Göttingen, starting (Chem. Eur. J. 2015, 21, 8812) with the designed amide 14, effected ortho metala­tion followed by coupling, to give the methylated product 15. Tetsuya Satoh and Masahiro Miura of Osaka University used (Org. Lett. 2015, 17, 704) the dithiane of 16 to direct ortho metalation. Coupling with acrylate followed by reductive desulfu­rization led to the ester 17. Jin-Quan Yu of Scripps/La Jolla designed (Angew. Chem. Int. Ed. 2015, 54, 888) the phenylacetamide 18 to direct selective meta metalation, leading to the unsat­urated aldehyde 19. In an extension of the Catellani protocol, Guangbin Dong of the University of Texas prepared (J. Am. Chem. Soc. 2015, 137, 5887) the biphenyl 21 by net meta metalation of the benzylamine 20. Several methods for the de novo assembly of benzene derivatives have recently been put forward. Rajeev S. Menon of the Indian Institute of Chemical Technology condensed (Org. Lett. 2015, 17, 1449) the unsaturated aldehyde 22 with the sulfonyl ester 23 to give 24.

Preparation of Benzene Derivatives: The Yu/Baran Synthesis of (+)-Hongoquercin A

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Electrophilic Aromatic Substitution ◽  
University Of Michigan ◽  
Aromatic Substitution ◽  
Blocking Group ◽  
University Of Texas ◽  
University Of Houston ◽  
National University ◽  
Reformatsky Reagent ◽  
The University

Lutz Ackermann of the Georg-August-Universität Göttingen oxidized (Org. Lett. 2013, 15, 3484) the anisole derivative 1 to the phenol 2. Melanie S. Sanford of the University of Michigan devised (Org. Lett. 2013, 15, 5428) complementary condi­tions for either para acetoxylation of 3, illustrated, to give 4, or meta acetoxylation. Lukas J. Goossen of the Technische Universität Kaiserlautern developed (Synthesis 2013, 45, 2387) conditions for the cascade alkoxylation/decarboxylation of 5 to give 6. Cheol-Hong Cheon of Korea University showed (J. Org. Chem. 2013, 78, 12154) that the boronic acid of 7 could act as a blocking group during electrophilic aromatic substitution or, as illustrated, as an ortho directing group. It could then be removed by protodeboronation, leading to 8. Jun Wu of Zhejiang University coupled (Synlett 2013, 24, 1448) the phenol 9 with the bromo amide 10 to give an ether that, on exposure to KOH at elevated temperature, rearranged to the intermediate amide, that was then hydrolyzed to 11. Dong-Shoo Shin of Changwon National University reported (Tetrahedron Lett. 2013, 54, 5151) a similar protocol (not illustrated) to prepare unsubsti­tuted anilines. Guangbin Dong of the University of Texas, Austin used (J. Am. Chem. Soc. 2013, 135, 18350) a variation on the Catellani reaction to add 13 to the ortho bromide 12 to give the meta amine 14. Kei Manabe of the University of Shizuoka found (Angew. Chem. Int. Ed. 2013, 52, 8611) that the crystalline N-for­myl saccharin 16 was a suitable CO donor for the carbonylation of the bromide 15 to the aldehyde 17. John F. Hartwig of the University of California, Berkeley described (J. Org. Chem. 2013, 78, 8250) the coupling of the zinc enolate of an ester (Reformatsky reagent), either preformed or generated in situ, with an aryl bromide 18 to give 19. Olafs Daugulis of the University of Houston developed (Org. Lett. 2013, 15, 5842) conditions for the directed ortho phenoxylation of 20 with 21 to give 22. Yao Fu of the University of Science and Technology of China effected (J. Am. Chem. Soc. 2013, 135, 10630) directed ortho cyanation of 23 with 24 to give 25.

Preparation of Benzene Derivatives: The Barrett Syntheses of Dehydroaltenuene B and 15G256β

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Aryl Halides ◽  
University Of Michigan ◽  
One Pot ◽  
Aromatic Carboxylates ◽  
Direct Functionalization ◽  
Aryl Tosylates ◽  
La Jolla ◽  
University Of Bristol ◽  
University Of Oslo ◽  
The University

Several new methods for the direct functionalization of Ar-H have appeared. Hisao Yoshida of Nagoya University observed (Chem. Comm. 2008, 4634) that under irradiation, TiO2 in water effected meta hydroxylation of benzonitrile 1 to give the phenol 2. Anisole showed ortho selectivity, while halo and alkyl aromatics gave mixtures. Melanie S. Sanford of the University of Michigan reported (J. Am. Chem. Soc. 2008, 130, 13285) a complementary study of Pd-catalyzed ortho acetoxylation. Jin-Quan Yu of Scripps/La Jolla developed (Angew. Chem. Int. Ed. 2008, 47, 5215) a Pd-catalyzed protocol for ortho halogenation of aromatic carboxylates such as 3. A related protocol (J. Am. Chem. Soc. 2008, 130, 17676) led to ortho arylation. Trond Vidar Hansen of the University of Oslo devised (Tetrahedron Lett. 2008, 49, 4443) a one-pot procedure for the net ortho cyanation of phenols such as 5 to the salicylnitrile 6. Robin B. Bedford of the University of Bristol, Andrew J. M. Caffyn of the University of the West Indies and Sanjiv Prashar of the Universidad Rey Juan Carlos established (Chem. Comm. 2008, 990) a Rh-catalyzed protocol for ortho arylation of phenols such as 7. Laurent Désaubry of the Université Louis Pasteur observed (Tetrahedron Lett. 2008, 49, 4588) regioselective coupling of unsymmetrical difluorobenzenes such as 9 to give the ether 10. Fuk Yee Kwong of Hong Kong Polytechnic University extended (Angew. Chem. Int. Ed. 2008, 47, 6402) Pd-mediated amination to the notoriously difficult mesylates, such as 11. John F. Hartwig of the University of Illinois reported (J. Am. Chem. Soc. 2008, 130, 13848) a related method for the amination of aryl tosylates. Hong Liu of the Shanghai Institute of Materia Medica found (Organic Lett. 2008, 10, 4513) that the Fe-catalyzed amination of aryl halides such as 13 sometimes gave mixtures of regioisomers. Hideki Yorimitsu and Koichiro Oshima of Kyoto University effected (Angew. Chem. Int. Ed. 2008, 47, 5833) Ag-catalyzed Grignard cross coupling with aryl halides, converting 15 into 16. Note that silyl aromatics such as 16 are readily reduced under dissolving metal conditions to give allyl silanes.

Stereocontrolled Construction of C-O Rings: The Seeberger/Hilvert Synthesis of KDN

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Aldol Condensation ◽  
Aromatic Aldehydes ◽  
Oxidative Cyclization ◽  
University Of Michigan ◽  
Relative Configuration ◽  
University Of Arizona ◽  
Acidic Conditions ◽  
The University ◽  
École Polytechnique ◽  
Simon Fraser University

Simple thought it appears, there has not been a good protocol for opening an epoxide 1 with a stabilized enolate. Ferdinando Pizzo of the Università di Perugia developed (Tetrahedron Lett. 2010, 51, 1566) a solution to this problem. Masahiro Terada of Tohoku University found (Angew. Chem. Int. Ed. 2010, 49, 1858) that under organocatalysis, the prochiral 4 condensed with aromatic aldehydes with high relative and absolute stereocontrol. Jon T. Njardarson, now at the University of Arizona, showed (Angew. Chem. Int. Ed. 2010, 49, 1648) that the geometry of the epoxide 7 dictated the relative configuration of the product dihydrofuran 8. John P. Wolfe of the University of Michigan devised (Organic Lett. 2010, 12, 1268) conditions for the diastereocontrolled cyclization of 9 to 10. Robert Britton of Simon Fraser University observed (Organic Lett. 2010, 12, 1716) that the microwave-induced closure of 12 proceeded with clean inversion. Christian B. W. Stark of the Universität Leipzig established ( Angew. Chem. Int. Ed. 2010, 49, 1587) that the Ru-mediated oxidative cyclization of 14 to 15 was also highly diastereocontrolled. Two all-trans diastereomers could emerge from the cascade aldol condensation of 16 with an aldehyde. Takashi Yamazaki of the Tokyo University of Agriculture and Technology devised (Organic Lett. 2010, 12, 268) conditions for the selective preparation of either diastereomer. Xuegong She of Lanzhou University uncovered (J. Am. Chem. Soc. 2010, 132, 1788) conditions for the Pt-mediated cyclization of the simple substrate 18 to the tetrahydropyran 19. Michael J. Zacuto of Merck Process established (Organic Lett. 2010, 12, 684) the Ru-catalyzed cyclization of 20 to 21. When an OH was not available, NH insertion was also efficient. Fabien Gagosz of the Ecole Polytechnique Palaiseau devised (J. Am. Chem. Soc. 2010, 132, 3543) the mechanistically distinct Au-mediated cyclization of 22 to 23. Glenn C. Micalizio of Scripps/Florida used (J. Am. Chem. Soc. 2010, 132, 7602) the protocol he had developed to couple 24 and 25 to give a intermediate trisubstituted alkene. Oxidative cleavage of the alkene delivered the ketone, which under acidic conditions cyclized to the spiroketal 26.

Metal-Mediated C–C Ring Construction: The Sun/Lin Synthesis of Huperzine A

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Conjugate Addition ◽  
Huperzine A ◽  
Ru Catalyst ◽  
Schwartz Reagent ◽  
Nef Reaction ◽  
Rice University ◽  
La Jolla ◽  
The University ◽  
École Polytechnique

Zachary T. Ball of Rice University found (Chem. Sci. 2014, 5, 1401) that the on-bead performance of a designed Rh- peptide complex was markedly superior to the corre­sponding solution catalysis for the addition of 2 to 1 to give 3. Jin-Quan Yu of Scripps/La Jolla achieved (J. Am. Chem. Soc. 2014, 136, 8138) remarkable ee in the conversion of 4 to 5. Adriaan J. Minnaard of the University of Groningen developed (Adv. Synth. Catal. 2014, 356, 2061) practical conditions for enantioselective conjugate addi­tion– enolate trapping, converting 6 to 8. Alexandre Alexakis of the University of Geneva had reported (Org. Lett. 2014, 16, 118) related results. Jérôme Waser of the Ecole Polytechnique Fédérale de Lausanne assembled (J. Am. Chem. Soc. 2014, 136, 6239) the amino cyclopentane 11 by adding 9 to 10. Jean-Luc Vasse of the Université de Reims used (Org. Lett. 2014, 16, 1506) the Schwartz reagent to cyclize 12 to 13. Eric V. Johnston and Armando Córdova of the University of Stockholm combined (Angew. Chem. Int. Ed. 2014, 53, 3447) Pd and organocatalysis in a cascade of first oxi­dation of 14, then conjugate addition by 15, then cyclization to 16. Professor Alexakis found (Org. Lett. 2014, 16, 2006) that the enolate from con­jugate addition to 17 could be trapped with a nitroalkene 18 to give, after in situ Nef reaction, the 1,4-diketone 19. Fangzhi Peng and Zhihui Shao of Yunnan University added (Chem. Eur. J. 2014, 20, 6112) malonate to the nitro alkene 20 to give an inter­mediate that could be carried to the cyclohexanone 21. Masahisa Nakada of Waseda University devised (Tetrahedron Lett. 2014, 55, 1100) a cascade conjugate reduc­tion—intramolecular conjugate addition to cyclize 22 to 23. Hye-Young Jang of Ajou University dimerized (Synthesis 2014, 46, 1329) cinnamaldehyde 24 with nitrometh­ane to give the fully-substituted cyclohexanol 25. In a remarkable cascade transformation, Joëlle Prunet of the University of Glasgow used (Org. Lett. 2014, 16, 3300) the Zhang Ru catalyst to cyclize 26 to the taxol skeleton 27. In an even more remarkable transformation, Professor Nakada showed (Tetrahedron Lett. 2014, 55, 1597) that cascade conjugate addition– conjugate addition converted 28 to 29, having the rare chair- boat- chair skeleton of the biologically potent fusidic acid and brasilicardin A.

Novae in the Magellanic Clouds

1979 ◽  
Vol 46 ◽  
pp. 96-101
Author(s):  
J.A. Graham
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
University Of Michigan ◽  
The Past ◽  
Spectroscopic Information ◽  
Objective Prism ◽  
The University ◽  
Small Cloud ◽  
Low Dispersion

During the past several years, a systematic search for novae in the Magellanic Clouds has been carried out at Cerro Tololo Inter-American Observatory. The Curtis Schmidt telescope, on loan to CTIO from the University of Michigan is used to obtain plates every two weeks during the observing season. An objective prism is used on the telescope. This provides additional low-dispersion spectroscopic information when a nova is discovered. The plates cover an area of 5°x5°. One plate is sufficient to cover the Small Magellanic Cloud and four are taken of the Large Magellanic Cloud with an overlap so that the central bar is included on each plate. The methods used in the search have been described by Graham and Araya (1971). In the CTIO survey, 8 novae have been discovered in the Large Cloud but none in the Small Cloud. The survey was not carried out in 1974 or 1976. During 1974, one nova was discovered in the Small Cloud by MacConnell and Sanduleak (1974).

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