Heteroaromatic Construction: The Wipf Synthesis of Cycloclavine

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
Vinyl Ketone ◽  
Methyl Vinyl ◽  
Cross Metathesis ◽  
University Of Oxford ◽  
Fe Catalyst ◽  
Normal University ◽  
La Jolla ◽  
The University ◽  
Technological University

Wesley J. Moran of the University of Huddersfield cyclized (Tetrahedron Lett. 2011, 52, 2605) a propargylated ketone 1 with Au to give the furan 2. Shengming Ma of the Shanghai Institute of Organic Chemistry found (Synlett 2011, 931) that tri(2-furyl)phosphine catalyzed the rearrangement of cyclopropene diesters, prepared by the addition of diazomalonate to alkynes, to the corresponding alkoxy furan 4. Xihe Bi and Qian Zhang of Northeast Normal University established (Chem. Commun. 2011, 47, 809) that a simple Fe catalyst effected the condensation of 5 with 6 to give the pyrrole 7. Gianfranco Favi of the Università degli Studi di Urbino showed (J. Org. Chem. 2011, 76, 2860) that the three-component coupling of 8 with an amine 9 and a ketone 10 proceeded without catalyst to deliver the pyrrole 11. Timothy J. Donohoe of the University of Oxford homologated (Org. Lett. 2011, 13, 1036) 12 by cross-metathesis with methyl vinyl ketone, to give, after oxidation and condensation with NH4OAc, the substituted pyridine 13. Dale L. Boger of Scripps/La Jolla condensed ( Org. Lett. 2011, 13, 2492) the unsubstitued 1,2,3-triazine 15 with an enamine 14 to give 16. Shunsuke Chiba of Nanyang Technological University prepared (J. Am. Chem. Soc. 2011, 133, 6411) the pyridine 19 by oxidizing the cyclopropanol 17 in the presence of the alkenyl azide 18. Limin Wang of the East China University of Science and Technology prepared (Tetrahedron Lett. 2011, 52, 509) the 2-aminopyridine 23 by the four-component coupling of the aldehyde 20 and the ketone 22 with NH4OAc and malononitrile 21. Taking advantage of the Knochel protocol for aryl Grignard formation, Christopher J. Moody of the University of Nottingham combined (Chem. Commun. 2011, 47, 788) the adduct from 24 with the ketone 25 to give the indole 26. Carsten Bolm of RWTH Aachen extended (Org. Lett. 2011, 13, 2012) the Fe catalysis reported by Zheng to the azide 27 to give 28. Sang-gi Lee of Ewha Womans University found (Org. Lett. 2011, 13, 1350) that the Blaise adduct from the addition of 29 to the nitrile could be cyclized to the indole 30.

Substituted Benzenes: The Garg Synthesis of Tubingensin A

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
University Of Pennsylvania ◽  
Ni Catalyst ◽  
Indiana University ◽  
Aryl Iodide ◽  
Shanghai Institute ◽  
Peking University ◽  
Normal University ◽  
La Jolla ◽  
The University

John F. Hartwig of the University of California, Berkeley devised (Science 2014, 343, 853) conditions for the regioselective silylation of an arene 1 to give 2. The silyl group can directly be converted, inter alia, to halo, amino, alkyl, or hydroxyl. Jin-Quan Yu of Scripps La Jolla effected (Angew. Chem. Int. Ed. 2014, 53, 2683) regioselective alkenylation of the arene 3 with 4 to give 5. Wei-Liang Duan of the Shanghai Institute of Organic Chemistry described (Org. Lett. 2014, 16, 500) a related alkenyl­ation protocol. Deping Wang of Henyang Normal University developed (Eur. J. Org. Chem. 2014, 315) inexpensive conditions for the conversion of an aryl bromide 6 to the corre­sponding phenol 7. Mamoru Tobisu and Naoto Chatani of Osaka University used (J. Am. Chem. Soc. 2014, 136, 5587) a Ni catalyst to convert the lactam 8 to the aryl boro­nate 9. Patrick J. Walsh of the University of Pennsylvania found (Adv. Synth. Catal. 2014, 356, 165) conditions for the clean monoarylation of the amide 11 with 10 to give 12. In an application of the Catellani approach, Zhi- Yuan Chen of Jiangxi Normal University coupled (Chem. Eur. J. 2014, 20, 4237) the aryl iodide 13 with 14 to give the amino ester 15. Frederic Fabis of the Université de Caen-Basse-Normandie used (Chem. Eur. J. 2014, 20, 7507) Pd to catalyze the ortho halogenation (and alkoxylation) of the N-sulfonylamide 16 to give 17. Wen Wan of Shanghai University and Jian Hao of Shanghai University and the Shanghai Institute of Organic Chemistry effected (Chem. Commun. 2014, 50, 5733) ortho azidination of the aniline 18 with 19, leading to 20. Jianbo Wang of Peking University found (Angew. Chem. Int. Ed. 2014, 53, 1364) that the N-aryloxy amide 21 could be combined with the α-diazo ester 22 to give the ortho-alkenyl phenol 23. Silas P. Cook of Indiana University uncovered (Org. Lett. 2014, 16, 2026) remarkably simple conditions for the enantiospecific cyclization of 24 (65% ee) to 25 (63% ee). The development of arynes as reactive intermediates continues unabated. Xiaoming Zeng of Xi’an Jiaotong University developed (Org. Lett. 2014, 16, 314) the reagent 27 for the bis-functionalization of the aryne derived from 26.

Low Catalyst Loading in the Cross Metathesis of Olefins with Methyl Vinyl Ketone

Synlett ◽  
2013 ◽  
Vol 24 (10) ◽  
pp. 1193-1196 ◽  
Author(s):  
Christian Slugovc ◽  
Muddasar Abbas ◽  
Anita Leitgeb
Keyword(s):  
Vinyl Ketone ◽  
Methyl Vinyl Ketone ◽  
Catalyst Loading ◽  
Methyl Vinyl ◽  
Cross Metathesis ◽  
The Cross ◽  
Low Catalyst Loading

Heteroaromatic Construction: The Fukuyama Synthesis of Tryprostatin A

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
University Of California ◽  
University Of Arkansas ◽  
Yale University ◽  
Au Catalyst ◽  
University Of Houston ◽  
Selective Substitution ◽  
Mcgill University ◽  
La Jolla ◽  
The University

Alessandro Palmieri of the University of Camerino developed (Synlett 2010, 2468) the condensation of a nitro acrylate 1 with a 1,3-dicarbonyl partner 2 to give the furan 3. Chaozhong Li of the Shanghai Institute of Organic Chemistry showed (Tetrahedron Lett. 2010, 51, 3678) that an alkenyl halide 4 could be cyclized to the furan 5. Ayhan S. Demir of Middle East Technical University established (Chem. Commun. 2010, 46, 8032) that a Au catalyst could catalyze the addition of an amine 7 to a cyanoester 6 to give the pyrrole 8 . Bruce A. Arndtsen of McGill University effected (Org. Lett. 2010, 12, 4916) the net three-component coupling of an imine 9, an acid chloride 10, and an alkyne 11 to deliver the pyrrole 12. Bernard Delpech of CNRS Gif-sur-Yvette prepared (Org. Lett. 2010, 12, 4760) the pyridine 15 by combining the diene 13 with the incipient carbocation 14. Max Malacria, Vincent Gandon, and Corinne Aubert of UPMC Paris optimized (Synlett 2010, 2314) the internal Co-mediated cyclization of a nitrile alkyne 5 to the tetrasubstituted pyridine 17. Yoshiaki Nakao of Kyoto University and Tamejiro Hiyama, now at Chuo University, effected (J. Am. Chem. Soc. 2010, 132, 13666) selective substitution of a preformed pyridine 18 at the C-4 position by coupling with an alkene 19. We showed (J. Org. Chem. 2010, 75, 5737) that the anion from deprotonation of a pyridine 21 could be added in a conjugate sense to 22 to give 23. Other particularly useful strategies for further substitution of preformed pyridines have been described by Olafs Daugulis of the University of Houston (Org. Lett. 2010, 12, 4277), by Phil S. Baran of Scripps/La Jolla (J. Am. Chem. Soc. 2010, 132, 13194), and by Robert G. Bergmann of the University of California, Berkeley, and Jonathan A. Ellman of Yale University (J. Org. Chem. 2010, 75, 7863). K. C. Majumdar of the University of Kalyani developed (Tetrahedron Lett. 2010, 51, 3807) the oxidative Pd-catalyzed cylization of 24 to the indole 25. Nan Zheng of the University of Arkansas showed (Org. Lett. 2010, 12, 3736) that Fe could be used to catalyze the rearrangement of the azirine 26 to the indole 27.

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.

Metal-Mediated C–C Ring Construction: The Carreira Synthesis of (+)-Asperolide C

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Conjugate Addition ◽  
Ring Expansion ◽  
Ethyl Acrylate ◽  
Heck Cyclization ◽  
University Of Oxford ◽  
Silyl Enol Ether ◽  
Emory University ◽  
Institute Of Technology ◽  
The University ◽  
Technological University

Djamaladdin G. Musaev and Huw M. L. Davies of Emory University effected (Chem. Sci. 2013, 4, 2844) enantioselective cyclopropanation of ethyl acrylate 2 with the α-diazo ester 1 to give 3 in high ee. Philippe Compain of the Université de Strasbourg used (J. Org. Chem. 2013, 78, 6751) SmI2 to cyclize 4 to the cyclobutanol 5. Jianrong (Steve) Zhou of Nanyang Technological University effected (Chem. Commun. 2013, 49, 11758) enantioselective Heck addition of 7 to the prochiral ester 6 to give the cyclopentene 8. Liu-Zhu Gong of USTC, Hefei added (Org. Lett. 2013, 15, 3958) the Rh enolate from the enantioselective ring expansion of the α-diazo ester 9 to the nitroalkene 10, to give 11 in high de. Stephen P. Fletcher of the University of Oxford set (Angew. Chem. Int. Ed. 2013, 52, 7995) the cyclic quaternary center of 14 by the enantioselective conjugate addition to 12 of the alkyl zirconocene derived from 13. Alexandre Alexakis of the University of Geneva reported (Chem. Eur. J. 2013, 19, 15226) high ee from the conjugate addition of alkenyl Al reagents (not illustrated) to 12. Paultheo von Zezschwitz of Philipps-Universität Marburg prepared (Adv. Synth. Catal. 2013, 355, 2651) the silyl enol ether 17 by trapping the intermediate from the conjugate addition of 16 to 15. Stefan Bräse of the Karlsruhe Institute of Technology effected (Eur. J. Org. Chem. 2013, 7110) conjugate addition to the prochiral dienone 18 to give the highly substi­tuted cyclohexenone 19. Ping Tian and Guo-Qiang Lin of the Shanghai Institute of Organic Chemistry cyclized (J. Am. Chem. Soc. 2013, 135, 11700) 20 to the kinetic, less stable epimer of the diketone 21. Rh-mediated intramolecular C–H insertion has been a powerful tool for the con­struction of cyclopentane derivatives. Douglass F. Taber of the University of Delaware found (J. Org. Chem. 2013, 78, 9772) that the Rh carbene derived from 22 was dis­criminating enough to target the more nucleophilic C–H bond, leading to the cyclohexanone 23. Kozo Shishido of the University of Tokushima observed (Org. Lett. 2013, 15, 3666) high diastereoselectivity in the intramolecular Heck cyclization of 24 to 25.

Heteroaromatics: The Zhou/Li Synthesis of Goniomitine

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
Oxidative Cyclization ◽  
Silyl Ether ◽  
Keto Ester ◽  
Transfer Protein ◽  
Shanghai Institute ◽  
Lanzhou Institute ◽  
Institute Of Technology ◽  
The University ◽  
Technological University

Xin-Yan Wu of East China University of Science and Technology and Jun Yang of the Shanghai Institute of Organic Chemistry added (Tetrahedron Lett. 2014, 55, 4071) the Grignard reagent 1 to propargyl alcohol 2 to give an intermediate that could be bory­lated, then coupled under Pd catalysis with an anhydride, leading to the furan 3. Fuwei Li of the Lanzhou Institute of Chemical Physics constructed (Org. Lett. 2014, 16, 5992) the furan 6 by oxidizing the keto ester 4 in the presence of the enamide 5. Yuanhong Liu of the Shanghai Institute of Organic Chemistry prepared (Angew. Chem. Int. Ed. 2014, 53, 11596) the pyrrole 9 by reducing the azadiene 7 with the Negishi reagent, then adding the nitrile 8. Yefeng Tang of Tsinghua University found (Tetrahedron Lett. 2014, 55, 6455) that the Rh carbene derived from 11 could be added to an enol silyl ether 10 to give the pyrrole 12. Pazhamalai Anbarasan of the Indian Institute of Technology Madras reported (J. Org. Chem. 2014, 79, 8428) related results. Zheng Huang of the Shanghai Institute of Organic Chemistry established (Angew. Chem. Int. Ed. 2014, 53, 1390) a connection between substituted piperidines and pyridines by dehydrogenating 13 to 15, with 14 as the acceptor. Joseph P. A. Harrity of the University of Sheffield conceived (Chem. Eur. J. 2014, 20, 12889) the cascade assembly of the pyridine 18 by cycloaddition of 16 with 17 followed by Pd-catalyzed coupling. Teck-Peng Loh of Nanyang Technological University converted (Org. Lett. 2014, 16, 3432) the keto ester 19 into the azirine, then eliminated it to form an aza­triene that cyclized to the pyridine 20. En route to a cholesteryl ester transfer protein inhibitor, Zhengxu S. Han of Boehringer Ingelheim combined (Org. Lett. 2014, 16, 4142) 21 with 22 to give an intermediate that could be oxidized to 23. Magnus Rueping of RWTH Aachen used (Angew. Chem. Int. Ed. 2014, 53, 13264) an Ir photoredox catalyst in conjunction with a Pd catalyst to cyclize the enamine 24 to the indole 25. Yingming Yao and Yingsheng Zhao of Soochow University effected (Angew. Chem. Int. Ed. 2014, 53, 9884) oxidative cyclization of 26 to 27.

Alkylated Stereogenic Centers: The Jia Synthesis of (−)-Goniomitine

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
Bimetallic Catalyst ◽  
The Other ◽  
Wild Type Enzyme ◽  
Enantiomerically Pure ◽  
Unsaturated Lactone ◽  
University Of Oxford ◽  
Stereogenic Centers ◽  
The University

John W. Wong of Pfizer and Kurt Faber of the University of Graz used (Adv. Synth. Catal. 2014, 356, 1878) a wild-type enzyme to reduce the nitrile 1 to 2 in high ee. Takafumi Yamagami of Mitsubishi Tanabe Pharma described (Org. Process Res. Dev. 2014, 18, 437) the practical diastereoselective coupling of the racemic acid 3 with the inexpensive pantolactone 4 to give, via the ketene, the ester 5 in high de. Takeshi Ohkuma of Hokkaido University devised (Org. Lett. 2014, 16, 808) a Ru/Li catalyst for the enantioselective addition of in situ generated HCN to an N-acyl pyrrole 6 to give 7 in high ee. Yujiro Hayashi of Tohoku University found (Chem. Lett. 2014, 43, 556) that an aldehyde 8 could be condensed with formalin, leading in high ee to the masked aldehyde 9. Stephen P. Fletcher of the University of Oxford prepared (Org. Lett. 2014, 16, 3288) the lactone 12 in high ee by adding an alkyl zirconocene, prepared from the alkene 11, to the unsaturated lactone 10. In a remarkable display of catalyst control, Masakatsu Shibasaki of the Institute of Microbial Chemistry and Shigeki Matsunaga of the University of Tokyo opened (J. Am. Chem. Soc. 2014, 136, 9190) the racemic aziridine 13 with malonate 14 using a bimetallic catalyst. One enantiomer of the aziridine was converted specifically to the branched product 15 in high ee. The other enantiomer of the aziridine was converted to the regioisomeric opening product. Kimberly S. Peterson of the University of North Carolina at Greensboro used (J. Org. Chem. 2014, 79, 2303) an enantiomerically-pure organophosphate to selec­tively deprotect the bis ester 16, leading to 17. Chunling Fu of Zhejiang University and Shengming Ma of the Shanghai Institute of Organic Chemistry showed (Chem. Commun. 2014, 50, 4445) that an organocatalyst could mediate the brominative oxi­dation of 18 to 19. The ee of the product was easily improved via selective crystalliza­tion of the derived dinitrophenylhydrazone. James P. Morken of Boston College developed (Org. Lett. 2014, 16, 2096) condi­tions for the allylation of an allylic acetate such as 20 with 21, to deliver the coupled product 22 with high maintenance of ee.

Organocatalytic Carbocyclic Construction: The Christmann Synthesis of (+)-Rotundial

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Central China ◽  
Dipolar Cycloaddition ◽  
The West ◽  
University Of Wisconsin ◽  
Facial Selectivity ◽  
Complementary Approach ◽  
Related Approach ◽  
Normal University ◽  
The University ◽  
Technological University

Karl Anker Jørgensen of Aarhus University found (Angew. Chem. Int. Ed. 2009, 48, 6650) that an organocatalyst could mediate the fragmentation of the prochiral cyclopropane 1 with high ee to the easily epimerized product 2. Guofu Zhong of Nanyang Technological University devised (Angew. Chem. Int. Ed. 2009, 48, 6089) a dipolar cycloaddition strategy for the organocatalyzed combination of 3 and 4 with PhNHOH to give the highly substituted cyclopentane 5. Professor Jørgensen also established (Angew. Chem. Int. Ed. 2009, 48, 7338) that conjugate addition of 7 to the prochiral cyclohexenone 6 proceeded with high ee. The initial adduct could be converted into the alkene 8, the alkyne, or the ketone. Wen-Jing Xiao of Central China Normal University, following up on the work of Gong and Cheng, developed (Tetrahedron 2009, 65, 9238) a simple organocatalyst for the desymmetrizing Michael addition of 9 to 10 to give 11 with high de and ee. Control of sidechain chirality is an important aspect of carbocyclic construction. Samuel H. Gellman of the University of Wisconsin demonstrated (J. Am. Chem. Soc. 2009, 131, 16018) that the organocatalyzed addition of 13 to 12 proceeded with high facial selectivity and excellent diastereocontrol. In a complementary approach, Alexander J. A. Cobb of the University of Reading optimized (J. Am. Chem. Soc. 2009, 131, 16016) an organocatalyst for the cyclization of 15 to 16, again with high facial selectivity and excellent diastereocontrol. Ying-Chun Chen of the West China School of Pharmacy established (Organic Lett. 2009, 11, 4660) conditions for the organocatalyzed combination of 17 with 18 to give 19. In a related approach, Bor-Cherng Hong of the National Chung Cheng University showed (Organic Lett. 2009, 11, 5246) that 20, 21, and 22 could be combined under organocatalysis to give 23 in high ee with excellent diastereocontrol. Both of these approaches, and several others that have been published recently, were carried out with aryl substituents. It remains to be seen whether alkyl substituents, which would be more useful in a target-directed synthesis, would be compatible with these methods for ring construction.

Developments in Alkene Metathesis

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Protein A ◽  
Ru Catalyst ◽  
Cross Metathesis ◽  
University Of Oxford ◽  
Ru Complex ◽  
Northwestern University ◽  
Allyl Sulfide ◽  
Aqueous Conditions ◽  
The University ◽  
Allyl Sulfides

Hervé Clavier and Steven P. Nolan, now at St. Andrew’s University, found (Adv. Synth. Cat. 2008, 350, 2959) that the indenylidene Ru complex 1 was an excellent pre-catalyst for alkene metathesis. A combination of 1 and the ligand 2 effected cross metathesis of 3 and 4 in just 15 minutes under microwave heating. Robert H. Grubbs of Caltech designed (Organic Lett. 2008, 10, 2693) the Ru catalyst 6 for the preparation of tri- and tetrasubstituted alkenes, as illustrated by the conversion of 7 to 8. The catalyst 6 also worked well for cross metathesis and ring opening metathesis polymerization (ROMP). For some biological applications, it would be desirable to run alkene cross metathesis under aqueous conditions. Benjamin G. Davis of the University of Oxford observed (J. Am. Chem. Soc. 2008, 130, 9642) that allyl sulfides such as 9 were unusually reactive in cross metathesis. Indeed, aqueous cross methathesis with such an allyl sulfide incorporated in a protein worked well, although added MgCl2 was required. The protein, a serine protease, maintained its activity after cross metathesis. α,β-Unsaturated thioesters such as 14 are excellent substrates for, inter alia, enantioselective Cu-catalyzed conjugate addition of Grignard reagents. Adriaan J. Minnaard and Ben L. Feringa of the University of Groningen found (J. Org. Chem. 2008, 73, 5651) that the thioacrylate 13 was an excellent substrate for cross methathesis, allowing ready preparation of 14 . Although alkene metathesis is often run in CH2Cl2 , benzene or toluene, these are not necessarily the optimal solvents. Siegfried Blechert of the TU Berlin established (Tetrahedron Lett. 2008, 49, 5968) that for the difficult cyclization of 16 to 17, hexafluorobenzene worked particularly well. The extended conformation (illustrated for 18) of an ester is more stable than the lactone conformation by about 5 kcal/mol. It is therefore not surprising that SonBinh T. Nguyen of Northwestern University observed (Organic Lett. 2008, 10, 5613) that attempted ring-closing metathesis of 18 gave only the dimer 20. On addition of the bulky Lewis acid 21, which can complex 18 in the lactone conformation, the reaction delivered the desired monomer 19. This should be a generally useful strategy for the cyclization of difficult ester substrates.

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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