Enantioselective Synthesis of Alcohols and Amines: The Zhu Synthesis of (+)-Trigonoliimine A

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Secondary Alcohol ◽  
Allylic Alcohol ◽  
Princeton University ◽  
Terminal Alkene ◽  
National University ◽  
Amino Amide ◽  
Enantioselective Epoxidation ◽  
Enantioselective Addition ◽  
Institute Of Technology ◽  
The University

The enantioselective epoxidation of a terminal alkene 1 has been a long-sought goal of organic synthesis. Albrecht Berkessel of the University of Cologne devised (Angew. Chem. Int. Ed. 2013, 52, 8467) a Ti catalyst that mediated the conversion of 1 to 2. Zhi Li of the National University of Singapore described (Chem. Commun. 2013, 49, 11572) a cell-based system that effected the enantioselective epoxidation of 3 to 4. Antonio Mezzetti of ETH Zürich and Francesco Santoro of Firmenich SA car­ried out (Angew. Chem. Int. Ed. 2013, 52, 10352) the enantioselective hydrogena­tion of 5 to the allylic alcohol 6. Elena Fernández of the Universitat Rovira i Virgilli and Andrew Whiting of Durham University devised (Org. Lett. 2013, 15, 4810) a protocol for the enantioselective conjugate borylation of the imine derived from 7, leading to the secondary alcohol 8. Benjamin List of the Max-Planck-Institute für Kohlenforschung, Mülheim and Choong Eui Song of Sungkyunkwan University con­densed (Angew. Chem. Int. Ed. 2013, 52, 12143) the thioester 10 with the aldehyde 9 to give the alcohol 11. Toshiro Harada of the Kyoto Institute of Technology developed (Org. Lett. 2013, 15, 4198) a general procedure for the enantioselective addition of a terminal alkene 12 to an aldehyde 9. As illustrated by the preparation of 13, this appears to be tolerant of a variety of organic functional groups. Professor Harada also established (Chem. Eur. J. 2013, 19, 17707) a protocol for the enantioselective addition of an alkyne 14 to an aldehyde to give the branched product 15. Chun-Jiang Wang and Xumu Zhang of Wuhan University hydrogenated (Angew. Chem. Int. Ed. 2013, 52, 8416) the alkyne 16 to the protected allylic amine 17. Keiji Maruoka of Kyoto University effected (J. Am. Chem. Soc. 2013, 135, 18036) the enantioselective α-amination of an aldehyde 18, to give 19. David W. C. MacMillan of Princeton University described (J. Am. Chem. Soc. 2013, 135, 11521) a comple­mentary approach, not illustrated. David J. Fox of the University of Warwick reduced (Chem. Commun. 2013, 49, 10022) the ketone 20, then rearranged the resulting sec­ondary alcohol to the α-amino amide 21.

Enantioselective Synthesis of Alcohols and Amines: The Ichikawa Synthesis of (+)-Geranyllinaloisocyanide

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Allylic Alcohol ◽  
Florida State University ◽  
State University ◽  
Quaternary Amine ◽  
National University ◽  
Cu Catalyst ◽  
Enantioselective Addition ◽  
Institute Of Technology ◽  
The University ◽  
University Of Manchester

Shuichi Nakamura of the Nagoya Institute of Technology reduced (Angew. Chem. Int. Ed. 2011, 50, 2249) the α-oxo ester 1 to 2 with high ee. Günter Helmchen of the Universität-Heidelberg optimized (J. Am. Chem. Soc. 2011, 133, 2072) the Ir*-catalyzed rearrangement of 3 to the allylic alcohol 4. D. Tyler McQuade of Florida State University effected (J. Am. Chem. Soc. 2011, 133, 2410) the enantioselective allylic substitution of 5 to give the secondary allyl boronate, which was then oxidized to 6. Kazuaki Kudo of the University of Tokyo developed (Org. Lett. 2011, 13, 3498) the tandem oxidation of the aldehyde 7 to the α-alkoxy acid 8. Takashi Ooi of Nagoya University prepared (Synlett 2011, 1265) the secondary amine 10 by the enantioselective addition of an aniline to the nitroalkene 9. Yixin Lu of the National University of Singapore assembled (Org. Lett. 2011, 13, 2638) the α-quaternary amine 13 by the addition of the aldehyde 11 to the azodicarboxylate 10. Chan-Mo Yu of Sungkyunkwan University added (Chem. Commun. 2011, 47, 3811) the enantiomerically pure 2-borylbutadiene 15 to the aldehyde 14 to give 16 in high ee. Because the allene is readily dragged out to the terminal alkyne, this is also a protocol for the enantioselective homopropargylation of an aldehyde. Lin Pu of the University of Virginia devised (Angew. Chem. Int. Ed. 2011, 50, 2368) a protocol for the enantioselective addition of 17 to the aldehyde 18 to give 19. Xiaoming Feng of Sichuan University developed (Angew. Chem. Int. Ed. 2011, 50, 2573) a Mg catalyst for the enantioselective addition of 21 to the α-oxo ester 20. Tomonori Misaka and Takashi Sugimura of the University of Hyogo added (J. Am. Chem. Soc. 2011, 133, 5695) 23 to 24 to give the Z-amide 25 in high ee. Marc L. Snapper and Amir H. Hoveyda of Boston College developed (J. Am. Chem. Soc. 2011, 133, 3332) a Cu catalyst for the enantioselective allylation of the imine 26. Jonathan Clayden of the University of Manchester effected (Org. Lett. 2010, 12, 5442) the enantioselective rearrangement of the amide 29 to the α-quaternary amine 30.

Enantioselective Construction of Alkylated Centers: The Shishido Synthesis of (+)-Helianane

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Allylic Alcohol ◽  
National University ◽  
Cu Catalyst ◽  
Rh Catalyst ◽  
Enantioselective Acylation ◽  
Enantioselective Addition ◽  
Institute Of Technology ◽  
Enantioselective Alkylation ◽  
Seoul National University ◽  
The University

Teck-Peng Loh of Nanyang Technological University developed (Org. Lett. 2011, 13, 876) a catalyst for the enantioselective addition of an aldehyde to the versatile acceptor 2 to give 3. Kirsten Zeitler of the Universität Regensburg employed (Angew. Chem. Int. Ed. 2011, 50, 951) a complementary strategy for the enantioselective coupling of 4 with 5. Clark R. Landis of the University of Wisconsin devised (Org. Lett. 2011, 13, 164) an Rh catalyst for the enantioselective formylation of the diene 7. Don M. Coltart of Duke University alkylated (J. Am. Chem. Soc. 2011, 133, 8714) the chiral hydrazone of acetone to give 9, then alkylated again to give, after hydrolysis, the ketone 11 in high ee. Youming Wang and Zhenghong Zhou of Nankai University effected (J. Org. Chem. 2011, 76, 3872) the enantioselective addition of acetone to the nitroalkene 12. Takeshi Ohkuma of Hokkaido University achieved (Angew. Chem. Int. Ed. 2011, 50, 5541) high ee in the Ru-catalyzed hydrocyanation of 15. Gregory C. Fu, now at the California Institute of Technology, coupled (J. Am. Chem. Soc. 2011, 133, 8154) the 9-BBN borane 18 with the racemic chloride 17 to give 19 in high ee. Scott McN. Sieburth of Temple University optimized (Org. Lett. 2011, 13, 1787) an Rh catalyst for the enantioselective intramolecular hydrosilylation of 20 to 21. Several general methods have been devised for the enantioselective assembly of quaternary alkylated centers. Sung Ho Kang of KAIST Daejon developed (J. Am. Chem. Soc. 2011, 133, 1772) a Cu catalyst for the enantioselective acylation of the prochiral diol 22. Hyeung-geun Park of Seoul National University established (J. Am. Chem. Soc. 2011, 133, 4924) a phase transfer catalyst for the enantioselective alkylation of 24. Peter R. Schreiner of Justus-Liebig University Giessen found (J. Am. Chem. Soc. 2011, 133, 7624) a silicon catalyst that efficiently rearranged the Shi-derived epoxide of 26 to the aldehyde 27. Amir H. Hoveyda of Boston College coupled (J. Am. Chem. Soc. 2011, 133, 4778) 28 with the alkynyl Al reagent 29 to give 30 in high ee. Kozo Shishido of the University of Tokushima prepared (Synlett 2011, 1171) 31 by the Mitsunobu coupling of m-cresol with the enantiomerically pure allylic alcohol.

Enantioselective Preparation of Alcohols and Amines

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Enantioselective Hydrogenation ◽  
Catalyst System ◽  
Hydroxy Ketone ◽  
Boston College ◽  
Princeton University ◽  
Terminal Alkene ◽  
Tokyo Institute ◽  
Enantioselective Addition ◽  
Institute Of Technology ◽  
The University

Renat Kadyrov of Evonik Degussa and Magnus Rueping of RWTH Aachen developed (Angew. Chem. Int. Ed. 2009, 49, 7556) an effective catalyst for the enantioselective hydrogenation of an α-hydroxy ketone 1 to the 1,2-diol 2 . Yong-Gui Zhou of the Dalian Institute of Chemical Physics showed (J. Org. Chem. 2009, 74, 5633) that a sultam such as 3 could be reduced with high ee to the sulfonamide 4. They also used this same approach to prepare both α-aryl and α,α-diaryl amines. David W. C. MacMillan of Princeton University described (Angew. Chem. Int. Ed. 2009, 49, 5121) the optimized enantioselective α-chlorination of an aldehyde 5 and the direct processing of the product to the epoxide 6. Erick M. Carreira of ETH Zürich reported (Synlett 2009, 2076) an alternative route to high ee epoxides by decarbonylation of an epoxy aldehyde 7. James P. Morken of Boston College established (J. Am. Chem. Soc. 2009, 131, 13210) a procedure for the enantioselective bis borylation of a terminal alkene 9, leading after oxidation to the 1,2-diol 10. Ben L. Feringa of the University of Groningen took advantage (J. Am. Chem. Soc. 2009, 131, 9473) of their alternative Wacker conditions to convert a primary allylic carbonate 11 to the protected β-amino aldehyde 12. Chao-Shan Da of Lanzhou University devised (Organic Lett. 2009, 11, 5578) additives that allow the direct enantioselective addition of a Grignard reagent 14 to an aldehyde. The enantioselective addition of substituted ketenes to aldehydes has long been established. Yun-Ming Lin of the University of Toledo developed (Synlett 2009, 1675) a catalyst system for the enantioselective addition of ketene 17 itself. An alkenyl silane 19 can readily be prepared from the corresponding terminal alkene (J. Org. Chem. 2010, 75, 1701). Koichi Mikami of the Tokyo Institute of Technology showed (J. Am. Chem. Soc. 2009, 131, 13922) that such alkenyl silanes add to ethyl glyoxylate 20 with high ee. Amir H. Hoveyda of Boston College devised (J. Am. Chem. Soc. 2009, 131, 18234) a procedure for the enantioselective conversion of a terminal alkyne 22 to the 1,2-bis boryl alkane, which he took on directly to the coupled product 24.

Functional Group Transformations

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Gold Catalyst ◽  
Sulfonyl Chloride ◽  
Allylic Alcohol ◽  
West Virginia University ◽  
Israel Institute ◽  
University Of Texas ◽  
Amino Amide ◽  
Cu Catalyst ◽  
Institute Of Technology ◽  
The University

Mark Gandelman of the Technion–Israel Institute of Technology devised (Adv. Synth. Catal. 2011, 353, 1438) a protocol for the decarboxylative conversion of an acid 1 to the iodide 3. Doug E. Frantz of the University of Texas, San Antonio effected (Angew. Chem. Int. Ed. 2011, 50, 6128) conversion of a β-keto ester 4 to the diene 5 by way of the vinyl triflate. Pei Nian Liu of the East China University of Science and Technology and Chak Po Lau of the Hong Kong Polytechnic University (Adv. Synth. Catal. 2011, 353, 275) and Robert G. Bergman and Kenneth N. Raymond of the University of California, Berkeley (J. Am. Chem. Soc. 2011, 133, 11964) described new Ru catalysts for the isomerization of an allylic alcohol 6 to the ketone 7. Xiaodong Shi of West Virginia University optimized (Adv. Synth. Catal. 2011, 353, 2584) a gold catalyst for the rearrangement of a propargylic ester 8 to the enone 9. Xue-Yuan Liu of Lanzhou University used (Adv. Synth. Catal. 2011, 353, 3157) a Cu catalyst to add the chloramine 11 to the alkyne 10 to give 12. Kasi Pitchumani of Madurai Kamaraj University converted (Org. Lett. 2011, 13, 5728) the alkyne 13 into the α-amino amide 15 by reaction with the nitrone 14. Katsuhiko Tomooka of Kyushu University effected (J. Am. Chem. Soc. 2011, 133, 20712) hydrosilylation of the propargylic ether 16 to the alcohol 17. Matthew J. Cook of Queen’s University Belfast (Chem. Commun. 2011, 47, 11104) and Anna M. Costa and Jaume Vilarrasa of the Universitat de Barcelona (Org. Lett. 2011, 13, 4934) improved the conversion of an alkenyl silane 18 to the iodide 19. Vinay Girijavallabhan of Merck/Kenilworth developed (J. Org. Chem. 2011, 76, 6442) a Co catalyst for the Markovnikov addition of sulfide to an alkene 20. Hojat Veisi of Payame Noor University oxidized (Synlett 2011, 2315) the thiol 22 directly to the sulfonyl chloride 23. Nicholas M. Leonard of Abbott Laboratories prepared (J. Org. Chem. 2011, 76, 9169) the chromatography-stable O-Su ester 25 from the corresponding acid 24.

Reactions of Alkenes

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Iron Catalyst ◽  
Catalytic Reduction ◽  
Indian Institute ◽  
Yale University ◽  
Terminal Alkene ◽  
National University ◽  
Institute Of Technology ◽  
La Jolla ◽  
The University

The catalytic reduction of the alkene 1 gave the cis-fused product (not illustrated), by kinetic H₂ addition to the less congested face of the alkene. Ryan A. Shenvi of Scripps La Jolla found (J. Am. Chem. Soc. 2014, 136, 1300) conditions for stepwise HAT, con­verting 1 to the thermodynamically-favored trans-fused ketone 2. Seth B. Herzon of Yale University devised (J. Am. Chem. Soc. 2014, 136, 6884) a protocol for the reduc­tion, mediated by 4, of the double bond of a haloalkene 3 to give the saturated halide 5. The Shenvi conditions also reduced a haloalkene to the saturated halide. Daniel J. Weix of the University of Rochester and Patrick L. Holland, also of Yale University, established (J. Am. Chem. Soc. 2014, 136, 945) conditions for the kinetic isomerization of a terminal alkene 6 to the Z internal alkene 7. Christoforos G. Kokotos of the University of Athens showed (J. Org. Chem. 2014, 79, 4270) that the ketone 9, used catalytically, markedly accelerated the Payne epoxidation of 8 to 10. Note that Helena M. C. Ferraz of the Universidade of São Paulo reported (Tetrahedron Lett. 2000, 41, 5021) several years ago that alkene epoxidation was also easily carried out with DMDO generated in situ from acetone and oxone. Theodore A. Betley of Harvard University prepared (Chem. Sci. 2014, 5, 1526) the allylic amine 12 by reacting the alkene 11 with 1-azidoadamantane in the presence of an iron catalyst. Rodney A. Fernandes of the Indian Institute of Technology Bombay developed (J. Org. Chem. 2014, 79, 5787) efficient conditions for the Wacker oxida­tion of a terminal alkene 6 to the methyl ketone 13. Yong-Qiang Wang of Northwest University oxidized (Org. Lett. 2014, 16, 1610) the alkene 6 to the enone 14. Peili Teo of the National University of Singapore devised (Chem. Commun. 2014, 50, 2608) conditions for the Markovnikov hydration of the alkene 6 to the alcohol 15. Internal alkenes were inert under these conditions, but Yoshikazo Kitano of the Tokyo University of Agriculture and Technology effected (Synthesis 2014, 46, 1455) the Markovnikov amination (not illustrated) of more highly substituted alkenes.

The Keck Synthesis of Epothilone B

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Total Synthesis ◽  
Secondary Alcohol ◽  
Allylic Alcohol ◽  
Ring Closing Metathesis ◽  
Relative Configuration ◽  
University Of Utah ◽  
Epothilone B ◽  
Hydride Reduction ◽  
Epothilone A ◽  
The University

The total synthesis of Epothilone B 4, the first natural product (with Epothilone A) to show the same microtubule-stabilizing activity as paclitaxel (Taxol®), has attracted a great deal of attention since that activity was first reported in 1995. The total synthesis of 4 devised (J. Org. Chem. 2008, 73, 9675) by Gary E. Keck of the University of Utah was based in large part on the stereoselective allyl stannane additions (e.g. 1 + 2 → 3 ) that his group originated. The allyl stannane 2 was prepared from the acid chloride 5. Exposure of 5 to Et3N generated the ketene, that was homologated with the phosphorane 6 to give the allene ester 7. Cu-mediated conjugate addition of the stannylmethyl anion 8 then delivered 2. The silyloxy aldehyde 1 was prepared from the ester 9 by reduction with Dibal. Felkincontrolled 1,2-addition of the allyl stannane 2 established the relative configuration of the secondary alcohol of 3, that was then used to control the relative configuration of the new alcohol in 10. Addition of the crotyl borane 12 to the derived aldehyde 11 also proceeded with high diastereocontrol. The other component of 4 was prepared from the aldehyde 14. Enantioselective allylation, by the method the authors developed, delivered the alcohol 16. The Z trisubstituted alkene was then assembled by condensing the aldehyde 17 with the phosphorane 18. Dibal reduction of the product lactone 19 gave a diol, the allylic alcohol of which was selectively converted to the chloride with the Corey-Kim reagent. Hydride reduction then delivered the desired homoallylic alcohol, that was converted to the phosphonium salt 21. Condensation of 21 with 13 gave the diene, that was carried on to Epothilone B 4. The synthesis of Epothilone B 4 as originally conceived by the authors depended on ring-closing metathesis of the triene 22. They prepared 22, but on exposure to the second-generation Grubbs catalyst it was converted only to 23. The authors concluded that the trans acetonide kept 22 in a conformation that did not allow the desired macrocyclization.

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.

Establishing Arrays of Stereogenic Centers: The Sato/Chida Synthesis of (-)-Kainic Acid

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Catalyst System ◽  
Allylic Alcohol ◽  
University Of Pennsylvania ◽  
Ni Catalyst ◽  
Max Planck ◽  
Stereogenic Centers ◽  
University College London ◽  
Enantioselective Addition ◽  
La Jolla ◽  
The University

Benjamin List of the Max-Planck-Institut, Mülheim, devised (J. Am. Chem. Soc. 2010, 132, 10227) a catalyst system for the stereocontrolled epoxidation of a trisubstituted alkenyl aldehyde 1. Takashi Ooi of Nagoya University effected (Angew. Chem. Int. Ed. 2010, 49, 7562; see also Org. Lett. 2010, 12, 4070) enantioselective Henry addition to an alkynyl aldehyde 3. Madeleine M. Joullié of the University of Pennsylvania showed (Org. Lett. 2010, 12, 4244) that an amine 7 added selectively to an alkynyl aziridine 6. Yutaka Ukaji and Katsuhiko Inomata of Kanazawa University developed (Chem. Lett. 2010, 39, 1036) the enantioselective dipolar cycloaddition of 9 with 10. K. C. Nicolaou of Scripps/La Jolla observed (Angew. Chem. Int. Ed. 2010, 49, 5875; see also J. Org. Chem. 2010, 75, 8658) that the allylic alcohol from enantioselective reduction of 12 could be hydrogenated with high diastereocontrol. Masamichi Ogasawara and Tamotsu Takahashi of Hokkaido University added (Org. Lett. 2010, 12, 5736) the allene 14 to the acetal 15 with substantial stereocontrol. Helen C. Hailes of University College London investigated (Chem. Comm. 2010, 46, 7608) the enzyme-mediated addition of 18 to racemic 17. Dawei Ma of the Shanghai Institute of Organic Chemistry, in the course of a synthesis of oseltamivir (Tamiflu), accomplished (Angew. Chem. Int. Ed. 2010, 49, 4656) the enantioselective addition of 21 to 20. Shigeki Matsunaga of the University of Tokyo and Masakatsu Shibasaki of the Institute of Microbial Chemistry developed (Org. Lett. 2010, 12, 3246) a Ni catalyst for the enantioselective addition of 23 to 24. Juthanat Kaeobamrung and Jeffrey W. Bode of ETH-Zurich and Marisa C. Kozlowski of the University of Pennsylvania devised (Proc. Natl. Acad. Sci. 2010, 107, 20661) an organocatalyst for the enantioselective addition of 27 to 26. Yihua Zhang of China Pharmaceutical University and Professor Ma effected (Tetrahedron Lett. 2010, 51, 3827) the related addition of 27 to 29. There have been scattered reports on the stereochemical course of the coupling of cyclic secondary organometallics. In a detailed study, Paul Knochel of Ludwig-Maximilians- Universität München showed (Nat. Chem. 2020, 2, 125) that equatorial bond formation dominated, exemplified by the conversion of 31 to 33.

Best Synthetic Methods: C-C Bond Construction

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Allylic Alcohol ◽  
Synthetic Methods ◽  
Grignard Reagents ◽  
Ni Catalyst ◽  
University Of Texas ◽  
University Of British Columbia ◽  
Terminal Alkene ◽  
Major Producer ◽  
The University ◽  
Linear Product

Nobuaki Kambe of Osaka University found (Tetrahedron Lett. 2009, 50, 5644) that with a Ni catalyst, Grignard reagents coupled preferentially with primary alkyl iodides, even in the presence of the usually reactive ketone. Maurice Santelli of the Université d’Aix-Marseille devised (Tetrahedron Lett. 2009, 50, 5238) a protocol for the conversion of a ketal 4 to the doubly homologated product 6. Brian T. Gregg of AMRI established (Tetrahedron Lett. 2009, 50, 3978; Tetrahedron Lett. 2009, 50, 7070) a procedure for the homologation of a nitrile 7 to the amine 9. Replacement of the NaBH4 with a second Grignard reagent led to the α-quaternary amine (not shown). Toshiaki Murai of Gifu University independently developed (J. Org. Chem. 2009, 74, 5703) a protocol for coupling two Grignard reagents with the linchpin reagent 11 to give the amine 12. Laurel L. Schafer of the University of British Columbia demonstrated (Angew. Chem. Int. Ed. 2009, 48, 8361) Ta-catalyzed intramolecular addition of a methyl amine 14 to the terminal alkene 13 to give 15. Jason S. Kingsbury of Boston College extended (Organic Lett. 2009, 11, 3202) the Roskamp protocol to unstable diazo alkanes such as 17, to give 18. Katsukiyo Miura of Saitama University found (Organic Lett. 2009, 11, 5066) that Pt catalyzed the branched addition of a terminal alkenyl silane 19 to an aldehyde 16 to give the branched adduct 20. Silanes such as 19 are readily prepared directly from the corresponding terminal alkene. Kálmán J. Szabó of Stockholm University observed (J. Org. Chem. 2009, 74, 5695) that the allyl boronate derived from the allylic alcohol 21 could add to the aldehyde 23 to give, depending on the solvent, either the branched product 24 or the linear product 25. The Wittig reaction is a major producer of by-product waste in chemical synthesis. Yong Tang of the Shanghai Institute of Organic Chemistry found (J. Org. Chem. 2007, 72, 6628) that Ph3As could serve catalytically in the condensation of 26 with an aldehyde. Christopher J. O’Brien of the University of Texas at Arlington and Gregory A. Chass of the University of Wales described (Angew. Chem. Int. Ed. 2009, 48, 6836) a related procedure using a cyclic phosphine.

Functional Group Transformation: The Castle Synthesis of Celogentin C

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Allylic Alcohol ◽  
Efficient Reduction ◽  
Simple Protocol ◽  
Peking University ◽  
Celogentin C ◽  
Purdue University ◽  
Institute Of Technology ◽  
Tertiary Amides ◽  
The University ◽  
Functional Group Transformation

Mark Cushman of Purdue University found (J. Org. Chem. 2010, 75, 3507) that a benzylic methyl ether 1 could be converted to the aldehyde 2 by N -bromosuccinimide. Two equivalents of NBS gave the methyl ester. Ning Jiao of Peking University used (Organic Lett. 2010, 12, 2888) NaN3 followed by DDQ to oxidize a benzylic halide 3 to the nitrile 4. Hugues Miel of Almac Sciences oxidized (Tetrahedron Lett. 2010, 51, 3216) the ketone 5 to the nitro derivative 6. The oxidative conversion of the nitro compound 7 to the ketone 8 described (Tetrahedron Lett. 2009, 50, 6389) by Vera L. Patrocinio Pereira of the Universidade Federal do Rio de Janeiro proceeded without epimerization. Sundarababu Baskaran of the Indian Institute of Technology Madras established (Angew. Chem. Int. Ed. 2010, 49, 804) that oxidative cleavage of the benzylidene acetal 9 delivered 10 with high regioselectivity. The intramolecular alkene dihydroxylation of 11 originated (Angew. Chem. Int. Ed. 2010, 49, 4491) by Erik J. Alexanian of the University of North Carolina gave 12 with high diastereocontrol. Ruimao Hua of Tsinghua University took advantage (J. Org. Chem. 2010, 75, 2966) of the H-donor properties of DMF to develop an efficient reduction of the alkyne 13 to the alkyne 14 . Alejandro F. Barrero of the University of Granada developed (J. Am. Chem. Soc. 2010, 132, 254) Ti (III) conditions for the reduction of the allylic alcohol 15 to the terminal alkene 16. Isolated alkenes were stable to these conditions. P. Veeraraghavan Ramachandran, also of Purdue University, effected (Tetrahedron Lett. 2010, 51, 3167) reductive amination of 17 to 18 using the now readily available NH3 - BH3 . Bin Ma and Wen-Cherng Lee of BiogenIdec developed (Tetrahedron Lett. 2010, 51, 385) a simple protocol for the conversion of an acid 19 to the free amine 20. Marc Lemaire of Université Lyons 1 established (Tetrahedron Lett. 2010, 51, 2092) that the silane 22 reduced primary, secondary, and tertiary amides to the aldehydes.

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