Academic literature on the topic 'P-Stereogenic catalysts'

Unsaturated half acid esters such as 1 are readily prepared by Stobbe condensation between dialkyl succinate and an aldehyde. Johannes G. de Vries of DSM and Floris P. J. T. Rutjes of Radboud University Nijmegen observed (Adv. Synth. Catal. 2008, 350, 85) that these acids were excellent substrates for enantioselective hydrogenation. Kazuaki Kudo of the University of Tokyo designed (Organic Lett. 2008, 10, 2035) a resin bound peptide catalyst for the transfer reduction of unsaturated aldehydes such as 3 , using 4 as the net H2 donor. Note that 5 was produced with high enantiocontrol from 3 that was a ~ 2:1 mixture of geometric isomers. Motomu Kanai and Masakatsu Shibasaki of the University of Tokyo devised (J. Am. Chem. Soc. 2008, 130, 6072) a chiral Gd catalyst that mediated the conjugate cyanation of enones such as 6 with high ee. Eric N. Jacobsen of Harvard University prepared (Angew. Chem. Int. Ed. 2008, 47, 1762) a dimeric Al salen catalyst that showed improved activity over the monomeric catalysts. Even congested imides such as 8 could be cyanated efficiently, delivering alkylated quaternary stereogenic centers. Takahiro Nishimura and Tamio Hayashi of Kyoto University optimized (J. Am. Chem. Soc. 2008, 130, 1576) the Rh*-catalyzed enantioselective conjugate addition of silyl acetylenes to enones such as 10, to give 12. Adriaan J. Minnaard and Ben L. Feringa of the University of Groningen devised (Angew. Chem. Int. Ed. 2008, 47, 398) conditions for the enantioselective 1,6-conjugate addition of alkyl Grignard reagents to diene esters such as the inexpensive ethyl sorbate 14. The product 16 incorporated, in addition to the newly formed stereogenic center, a geometrically defined E alkene. William S. Bechara and André B. Charette of the Université de Montréal found (Organic Lett. 2008, 10, 2315) that alkyl Grignard reagents could be induced to add with high enantioselectivity to pyridyl sulfones such as 17. In a different approach, Gregory C. Fu of MIT developed (J. Am. Chem. Soc. 2008, 130, 3302; J. Am. Chem. Soc. 2008, 130, 2756) conditions for the enantioselective alkenylation of racemic bromo esters such as 19, The latter reference is to the analogous enantioselective coupling of organozinc bromides with racemic allylic chlorides.

Powerful methods for catalytic, enantioselective intermolecular Diels-Alder reactions have been developed. Ben L. Feringa and Gerard Roelfes of the University of Groningen have shown (Organic Lett. 2007, 9, 3647) that a catalyst prepared by combining salmon testes DNA with a Cu complex directed the absolute sense of the addition of 1 to cyclopentadiene 2 . Mukund P. Sibi of North Dakota State University has reported (J. Am. Chem. Soc . 2007, 129 , 395) related work with achiral pyrazolidinone dienophiles and chiral Cu catalysts. Tohru Fukuyama of the University of Tokyo found (Angew. Chem. Int. Ed . 2007, 46, 5734) that the MacMillan catalyst 5 was effective at mediating the addition of acrolein 4 to the pyridine-derived diene 3, enabling an enantioselective synthesis of the prominent antiviral (-)-oseltamivir (tamiflu) 7. Hisashi Yamamoto of the University of Chicago has demonstrated (J. Am. Chem. Soc . 2007, 129, 9534 and 9536) that the novel catalyst 10 effected addition of methyl acrylate 9 to the diene 8, leading to an elegant enantioselective synthesis of the tetracycle 12, the key intermediate in the Nicolaou synthesis of platensimycin. New illustrations of the power of the intramolecular Diels-Alder reaction have been put forward. Demonstrating the influence of a single subsituent on the tether, William R. Roush of Scripps/Florida found (Organic Lett . 2007, 9, 2243) that cyclization of 13 led to the diastereomer 14, complementary to the result observed with an acyclic triene. Ryo Shintani and Tamio Hayashi of Kyoto University have extended (Angew. Chem. Int. Ed . 2007, 46, 7277) their studies of chiral diene-based Rh catalysts to the enantioselective cyclization of alkynyl dienes such as 16. Jonathan W. Burton of the University of Oxford and Andrew B. Holmes of the University of Melbourne employed (Chem. Commun . 2007, 3954) the MacMillan catalyst 5 for the cyclization of 18 to 19. It is impressive that ent- 5 catalyzed the cyclization of 18 cleanly into the diastereomer of 19 in which both of the newly-created stereogenic centers were inverted.

Kami L. Hull of the University of Illinois established (J. Am. Chem. Soc. 2014, 136, 11256) conditions for the diastereoselective hydroamination of 1 with 2 to give 3. Jon C. Antilla of the University of South Florida employed (Org. Lett. 2014, 16, 5548) an enantiomerically-pure Li phosphate to direct the opening of the prochiral epoxide 4 to 5. Jordi Bujons and Pere Clapés of IQAC-CSIC engineered (Chem. Eur. J. 2014, 20, 12572) an enzyme that mediated the enantioselective addition of glycolaldehyde 7 to an aldehyde 6, leading to 8. Takahiro Nishimura of Kyoto University set (J. Am. Chem. Soc. 2014, 136, 9284) the two stereogenic centers of 11 by adding 10 to the diene 9. Amir H. Hoveyda of Boston College added (J. Am. Chem. Soc. 2014, 136, 11304) the propargylic anion derived from 13 to the aldehyde 12 to give, after oxida­tion, the diol 14. Yujiro Hayashi of Tohoku University constructed (Adv. Synth. Catal. 2014, 356, 3106) 17 by the combination of 15 with 16. Yitzhak Apeloig and Ilan Marek of Technion-Israel Institute of Technology prepared (J. Org. Chem. 2014, 79, 12122) the bromo diol 20 by rearranging the adduct between the alkyne 19 and the acyl silane 18. James P. Morken, also of Boston College, effected (J. Am. Chem. Soc. 2014, 136, 17918) enantioselective coupling of 22 with the bis-borane 21. The prod­uct allyl borane added to benzaldehyde to give the alcohol 23. Sentaro Okamoto of Kanagawa University reduced (Org. Lett. 2014, 16, 6278) the aryl oxetane 24 to an intermediate that coupled with allyl bromide to give the alco­hol 25. In the presence of catalytic CuCN, the alternative diastereomer was the major product. Erick M. Carreira of ETH Zürich used (Angew. Chem. Int. Ed. 2014, 53, 13898) a combination of an Ir catalyst and an organocatalyst to couple the aldehyde 27 with the allylic alcohol 26. The four possible combinations of enantiomerically pure catalysts worked equally well, enabling the preparation of each of the four enan­tiomerically pure diastereomers of 28.

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.

Sunggak Kim of KAIST reported (Synlett 2009, 81) an improved protocol for the one-carbon free radical homologation of an iodide such as 1 to the nitrile. Primary, secondary, and tertiary iodides work well. We described (Tetrahedron Lett. 2009, 50, 2462) a procedure for the one-carbon homologation of a halide 4 directly to the benzyl ether 6. Bin Xu of Shanghai University showed (Chem. Commun. 2009, 3246) that conversion of a ketone 8 to the 1,1-dibromoalkene set the stage for the net one-carbon homologation to the amide 9. A. Fernández-Mateos of the Universidad de Salamanca uncovered (J. Org. Chem. 2009, 74, 3913) a powerful new branching reaction, condensing the more substituted center of an epoxide 10 with a nitrile 11 to deliver the adduct 12. Useful diastereocontrol was observed with cyclic epoxides. Uli Kazmaier of the Universität des Saarlandes optimized (Adv. Synthy. Cat. 2009, 351, 1395) a Mo catalyst for the hydrostannation of a terminal alkene 13 to the branched product 14. Dong-Mei Cui of the Zhejiang University of Technology and Chen Zhang of Zhejiang University (both in Hangzhou) developed (Chem. Commun. 2009, 1577) a complementary procedure, converting the terminal alkene 15 into the branched alkenyl tosylate 16. The Wittig reaction is notorious for racemizing sensitive aldehydes. Hélène Lebel of the Université de Montréal demonstrated (Organic Lett. 2009, 11, 41) a simple one-pot protocol for sequential oxidation and homologation of 17 that preserved the integrity of the adjacent stereogenic center. The stereocontrolled construction of trisubstituted alkenes is still a major issue in organic synthesis. Giancarlo Verardo of the University of Udine established (J. Phys. Org. Chem. 2009, 22, 24) that the α-diazo ester 19, readily prepared directly from the simple ester, was converted by I2 to the alkene 20 with high geometric control. Condensation with the Ohira reagent 22 is often the method of choice for converting an aldehyde into the homologated alkyne. Hubert Maehr and Milan Uskokovic of Bioxell and Carl P. Schaffner of the Waksman Institute described (Syn. Commun. 2009, 39, 299) an optimized, scalable procedure for the in situ preparation of 22 and the conversion of 21 to 23. Note, again, that the sensitive stereogenic center adjacent to the intermediate aldehyde was not epimerized under the reaction conditions.

Jon D. Stewart of the University of Florida established (Chem. Commun. 2010, 46, 8558) a scalable enzymatic reduction of geranial 1 to citronellal 2. Andreas S. Bommarius of Georgia Tech reported (Chem. Commun. 2010, 46, 8809) related studies. Isamu Shiina of the Tokyo University of Science developed (J. Am. Chem. Soc. 2010, 132, 11629) a nucleophilic catalyst for the kinetic resolution of α-chiral carboxylic acids such as 3. David W. C. MacMillan of Princeton University devised (J. Am. Chem. Soc. 2010, 132, 13600) a protocol for the enantioselective benzylation of an aldehyde 5. Kian L. Tan of Boston College (J. Am. Chem. Soc. 2010, 132, 14757) and Shannon S. Stahl and Clark R. Landis of the University of Wisconsin (J. Am. Chem. Soc. 2010, 132, 14027) developed the regioselective enantioselective hydroformylation of alkenes such as 7 with chelating substituents. Masaya Sawamura of Hokkaido University (J. Am. Chem. Soc. 2010, 132, 879) and others (Org. Lett. 2010, 12, 2438; Tetrahedron Lett. 2010, 5592, 6018) effected enantiospecific allylic coupling, as in the conversion of 9 to 10 . James P. Morken, also of Boston College, achieved (J. Am. Chem. Soc. 2010, 132, 10686) enantioselective allylation of 11. Ben L. Feringa of the University of Groningen devised (J. Am. Chem. Soc. 2010, 132, 13152) a protocol for net enantioselective conjugate addition to an α, β-unsaturated alde hyde 14. Gary A. Molander of the University of Pennsylvania found (J. Am. Chem. Soc. 2010, 132, 17108) that coupling of 16, prepared by enantioselective conjugate addition, proceeded with inversion. Naoya Kumagai and Masakatsu Shibasaki of the Institute of Microbial Chemistry effected (J. Am. Chem. Soc. 2010, 132, 10275) enantioselective alkynylation of the thioamide 18, and Takahiro Nishimura and Tamio Hayashi of Kyoto University achieved (Chem. Commun. 2010, 46, 6837) conjugate alkynylation of the nitroalkene 20. Several other protocols (Angew. Chem. Int. Ed. 2010, 49, 5780, 7299, 8145; J. Am. Chem. Soc. 2010, 132, 14373; J. Org. Chem. 2010, 75, 7829) have been developed for the catalytic enantioselective construction of arylated stereogenic centers.

Naoki Toyooka of the University of Toyama prepared (Eur. J. Org. Chem. 2013, 2841) the lactam 1 from commercial tri-O-benzyl-D-glucal. Reduction with Dibal followed by coupling of the intermediate with allyltrimethylsilane delivered the piper­idine 2, that was carried on to (−)-L-batzellaside A 3. Ronalds Zemribo of the Latvian Institute of Organic Synthesis effected (Org. Lett. 2013, 15, 4406) Ireland–Claisen rearrangement of the lactone 4 to give the pyrroli­dine 5 with high geometric control. This was readily converted to limazepine E 6. Sunil V. Pansare of Memorial University used (Synthesis 2013, 45, 1863) an organo­catalyst to set the relative and absolute configuration in the addition of 7 to 8 to give 9. The acyclic stereogenic center of 9 was inverted twice en route to (+)-febrifugine 10. Uttam K. Tambar of the University of Texas Southwestern Medical Center combined (Org. Lett. 2013, 15, 5138) 11 with 12 under Pd catalysis to set the rel­ative configuration of 13. Late-stage bromination completed the synthesis of amathaspiramide F 14. Richard C. D. Brown of the University of Southampton used (Org. Lett. 2013, 15, 4596) the sulfinylimine of 15 to direct the stereochemical sense of the addition of 16. The product 17 was carried over several steps to the tetracyclic alkaloid allomatrine 18. Stephen P. Waters of the University of Vermont devised (Org. Lett. 2013, 15, 4226) what appears to be a general route to pyridones. On warming, the acyl azide derived from the acid 19 rearranged to the isocyanate, that cyclized to the pyridone 20. Deprotection led to the Lycopodium alkaloid lyconadin C 21. Among the several creative routes to indole alkaloids that have been put forward in recent months, the synthesis of tabersonine 25 (J. Am. Chem. Soc. 2013, 135, 13334) by Rodrigo B. Andrade of Temple University stands out. Deprotonation of 22 led to an anion that was condensed with 23 to give 24, with the relative and absolute configuration directed by the pendant sulfinylimine. In addition to tabersonine, the intermediate 24 was carried on to vincadifformine and to aspidospermidine.