Academic literature on the topic 'Chiral epoxides; Alkenes; Organic synthesis'

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.

One of the most powerful of alkene transformations is enantioselective epoxidation. Tsutomu Katsuki of Kyushu University has developed (Angew. Chem. Int. Ed. 2007, 46, 4559) a Ti catalyst that with H2O2, selectively epoxidized terminal alkenes with high ee. The same catalyst converted a Z 2-alkene such as 3 into the epoxide. This is significant, because such epoxides are opened with nucleophiles selectively at the less congested center. Novel procedures for alkene functionalization have been put forward. Philippe Renaud of the University of Berne has developed (Adv. Synth. Cat. 2008, 350, 1163) a simple protocol for terminal halogenation, based on catalyzed addition of catecholborane, followed by free radical substitution. Sulfides and selenides were also prepared. H. Zoghlami of the Faculty of Sciences of Tunis has devised (Tetrahedron Lett. 2007, 48, 5645) an oxidative sulfinylation, converting a terminal alkene 7 to the sulfide 8. M. Christina White of the University of Illinois (J. Am. Chem. Soc. 2008, 130, 3316) and Guosheng Liu of the Shanghai Institute of Organic Chemistry (Angew. Chem. Int. Ed. 2008, 47, 4733) independently developed Pd catalysts for the oxidation of a terminal alkene 9 to the terminal allylic amine 10. Shannon S. Stahl of the University of Wisconsin-Madison has established (Organic Lett. 2007, 9, 4331) conditions for the complementary transformation of a terminal alkene 11 to the enamide 12. Douglas B. Grotjahn of San Diego State University has optimized (J. Am. Chem. Soc. 2007, 129, 9592) Ru-catalyzed alkene (“zipper”) migration, effecting the conversion of 13 to 14 and of 15 to 16 . There have been several new observations on alkene cleavage. Marcus A. Tius of the University of Hawaii and Bakthan Singaram of the University of California, Santa Cruz have found (Tetrahedron Lett. 2008, 49, 2764) that epoxides such as 17 are cleaved directly by NaIO4, providing a simple alternative to ozonolysis. Rolando A. Spanevello of the Universidad Nacional de Rosario has extended (Tetrahedron 2007, 63, 11410) unsymmetrical ozonolysis to highly substituted norbornene derivatives such as 19, observing 20 as the only product. Patrick H. Dussault of the University of Nebraska–Lincoln has established (J. Org. Chem. 2008, 73, 4688) that alkene ozonolysis in wet acetone delivered the ketone or aldehyde directly, without reductive workup.

The α-C–H functionalization of piperidine catalyzed by tantalum complex 1 to pro­duce amine 2 was developed (Org. Lett. 2013, 15, 2182) by Laurel L. Schafer at the University of British Columbia. An asymmetric diamination of diene 3 with diaziri­dine reagent 4 under palladium catalysis to furnish cyclic sulfamide 5 was developed (Org. Lett. 2013, 15, 796) by Yian Shi at Colorado State University. Enantioenriched β-fluoropiperdine 8 was prepared (Angew. Chem. Int. Ed. 2013, 52, 2469) via amino­fluorocyclization of 6 with hypervalent iodide 7, as reported by Cristina Nevado at the University of Zurich. Erick M. Carreira at ETH Zürich disclosed (J. Am. Chem. Soc. 2013, 135, 6814) a ruthenium-catalyzed hydrocarbamoylation of allylic formamide 9 to yield pyrrolidone 10. Hans-Günther Schmalz at the University of Köln disclosed (Angew. Chem. Int. Ed. 2013, 52, 1576) an asymmetric hydrocyanation of styrene 11 with Ni(cod)₂ and phosphine–phosphite ligand 12 to yield exclusively the branched cyanide 13. A simi­lar transformation of styrene 11 to the hydroxycarbonylated product 15 was catalyzed (Chem. Commun. 2013, 49, 3306) by palladium complex 14, as reported by Matthew L. Clarke at the University of St Andrews. Feng-Ling Qing at the Chinese Academy of Sciences found (Angew. Chem. Int. Ed. 2013, 52, 2198) that the hydrotrifluoromethylation of unactivated alkene 16 to 17 was catalyzed by silver nitrate. The same transformation was also reported (J. Am.Chem. Soc. 2013, 135, 2505) by Véronique Gouverneur at the University of Oxford using a ruthenium photocatalyst and the Umemoto reagent 18. Clark R. Landis at the University of Wisconsin, Madison reported (Angew. Chem. Int. Ed. 2013, 52, 1564) a one-pot asymmetric hydroformylation using 21 followed by Wittig olefination to transform alkene 19 into the γ-chiral α,β-unsaturated carbonyl compound 20. Debabrata Mati at the Indian Institute of Technology Bombay found (J. Am. Chem. Soc. 2013, 135, 3355) that alkene 22 could be nitrated stereoselectively with silver nitrite and TEMPO to form alkene 23. Damian W. Young at the Broad Institute disclosed (Org. Lett. 2013, 15, 1218) that a macrocyclic vinylsiloxane 24, which was synthesized via an E-selective ring clos­ing metathesis reaction, could be functionalized to make either E- or Z-alkenes, 25 and 26.

Several new developments in enantioselective C-O ring construction have been applied in the syntheses of natural products. To achieve control, the oxygenated quaternary center of dysiherbaine 9 must be established under kinetic conditions. One approach would be SN2 opening, but this would require displacement at a fully-substituted center. Susumi Hatakeyama of Nagasaki University has shown (Chem. Commun. 2007, 4158) that the epoxide 6, prepared by the Sharpless procedure, undergoes just such an opening under mild acid catalysis. Another approach to highly-substituted tetrahydrofurans and tetrahydropyrans is to join two carbons of a preformed chiral ether, such as 18. This is the strategy that István E. Markó employed in his recent (J. Am. Chem. Soc. 2007, 129, 3516) synthesis of jerangolid D 22. The key step was the three-component coupling of 15, 16, and 17, using a protocol recently developed in his group. Again using a procedure his group had developed, the trisubstituted alkene of 21 was prepared by modified Julia coupling of the ketone 19 with the anion of sulfone 20, followed be esterification and reduction. The spiroketal ( + )-spiroxaline methyl ether 31 contains three secondary oxygenated stereogenic centers. In a showcase of current chiral technology, Barry M. Trost of Stanford University constructed (Angew. Chem. Int. Ed. 2007, 46, 7664) the first two of the three alcohols by the enantioselective addition of an alkyne to an aldehyde. The chiral catalyst 25 that directed the alkyne additions was derived from a commercial ligand. The last alcohol center was derived from R -( + )-epoxypropane. Note that the spiroketal was not prepared in the usual way, by acid-catalyzed cyclization of a dihydroxy ketone, but by Pd-catalyzed cyclization of the alkyne diol 30.

Enantiomerically-pure natural amino acids can serve as starting materials for alkaloid synthesis. In his synthesis (J. Org. Chem. 2007, 72, 10114) of (-)-α-kainic acid 3, Kyung Woon Jung of the University of Southern California prepared the diazo sulfone 1 from (L)-glutamic acid. Rh-mediated intramolecular C-H insertion proceeded with the predicted high diastereoselectivity, to give the lactam 2, containing seven of the ten carbon atoms and two of the three stereogenic centers of (-)-α-kainic acid 3. The absolute configuration of the nitrogen ring system(s) can also be established by chiral catalysis. Dawei Ma of the Shanghai Institute of Organic Chemistry has developed (J. Am. Chem. Soc. 2007, 129, 9300) a chiral Cu catalyst that mediated the addition of alkynyl esters and ketones to the prochiral acylated pyridine 4 in high enantiomeric excess. The dihydro-pyridines (e.g. 5) so produced will be versatile starting materials both for alkaloid synthesis, as illustrated by the preparation of the Dendrobatid alkaloid 223AB 6, and for the production of pharmaceuticals. In his synthesis of the Dentrobatid alkaloid pumiliotoxin 251D 9, Timothy F. Jamison took (J. Org. Chem. 2007, 72, 7451) as his starting material another amino acid, proline. Ni-mediated cyclization of the epoxide 8 proceeded with high geometric and regiocontrol, to give 9. The chemistry to convert 7 into 8 with high diastereocontrol and without racemization is a substantial contribution that will have many other applications. In his synthesis (Organic Lett. 2007, 9, 2763) of spirotryprostatin B 12, Barry M. Trost of Stanford University also started with proline, which was readily elaborated to the oxindole 10. The question was, could the Pd-catalyzed decarboxylation of 10 be induced to provide specifically 11? Counting geometric isomers of the trisubstituted alkene, and allylic regioisomers, as well as diastereomers, there were sixteen possible products from this prenylation. Using chiral Pd control, the rearrangement proceeded with 14:1 regiocontrol, and 16:1 diasterocontrol. Oxidative cyclization of 11 then delivered spirotryprostatin B 12. The Cephalotaxus alkaloid (-)-drupacine 19 has five stereogenic centers, including four of the five positions on the cyclopentane ring.

Hisashi Yamamoto of the University of Chicago and Chubu University developed (J. Am. Chem. Soc. 2014, 136, 1222) a tungsten catalyst for the enantioselective oxida­tion of allylic alcohols such as 1 to the epoxide 2. Homoallylic alcohols also worked well. Naoya Kumagai and Masakatsu Shibasaki of the Institute of Microbial Chemistry devised (Chem. Eur. J. 2014, 20, 68) a scalable Zn-catalyzed protocol for the coupling of 3 with 4 to give 5. Professor Shibasaki and Takumi Watanabe, also of the Institute of Microbial Chemistry, established (Org. Lett. 2014, 16, 3364) a Nb catalyst for the preparation of 8 by the Henry addition of 7 to 6. Wenhao Hu of East China Normal University effected (Synthesis 2014, 46, 1348) the coupling of 9 and 10 with two equivalents of aniline to give the diamine 10. Sanzhong Luo of the Institute of Chemistry, Beijing showed (Angew. Chem. Int. Ed. 2014, 53, 4149) that the adduct between 11 and an in situ formed N-nitroso could be reduced with high diastereoselectivity, leading to 12. Kumagai and Shibasaki also described (Angew. Chem. Int. Ed. 2014, 53, 5327) the assembly of 15 by the enantiose­lective addition 14 to 13. Bernhard Breit of the Albert-Ludwigs-Universität Freiburg effected (Synthesis 2014, 46, 1311) the carbonylation of the alkene 16 to give an alde­hyde that underwent in situ condensation with the imine 17, leading, after a subse­quent addition of vinyl magnesium chloride, to the lactone 18. Michael J. Krische of the University of Texas prepared (J. Am. Chem. Soc. 2014, 136, 8911) the diol 21 by adding the racemic epoxide 20 to the aldehyde 19. Martin Hiersemann of the Technische Universität Dortmund achieved (J. Org. Chem. 2014, 79, 3040) high enantioselectivity in the rearrangement of the enol ether 22 to 23. Michael T. Crimmins also observed (Org. Lett. 2014, 16, 2458) high ste­reocontrol in the rearrangement of 24 to 25. Wannian Zhang and Chunquan Sheng of the Second Military Medical University and Wei Wang of the University of New Mexico and the East China University of Science and Technology added (Org. Lett. 2014, 16, 692) the diketone 26 to the aldehyde 6 to give an intermediate adduct, that further cyclized to 27.

Yao Fu and Lei Liu of the University of Science and Technology of China devised (Chem. Eur. J. 2014, 20, 15334) conditions for the coupling of a halide 2 with a tosyl­ate 1 with inversion of absolute configuration, leading to 3. Hegui Gong of Shanghai University coupled (J. Am. Chem. Soc. 2014, 136, 17645) the glucosyl bromide 4 with an anhydride 5 to give the ketone 6. Luigi Vaccaro of the Università di Perugia showed (Org. Lett. 2014, 16, 5721) that TBAF promoted the opening of the epoxide 7 with the ketene silyl acetal 8, leading to the lactone 9. Valérie Desvergnes and Yannick Landais of the University of Bordeaux assembled (Chem. Eur. J. 2014, 20, 9336) the diketone 12 by using a Stetter catalyst to promote the conjugate addition of the acyl silane 11 to the enone 10. Thomas Werner of the Leibniz-Institute for Catalysis reported (Eur. J. Org. Chem. 2014, 6873) the enantioselective conversion of the prochiral triketone 13 to the bicyclic enone 15 by an intramolecular Wittig reaction, mediated by 14. Elizabeth H. Krenske of the University of Queensland and Christopher J. O’Brien also reported (Angew. Chem. Int. Ed. 2014, 53, 12907) progress (not illustrated) on catalytic Wittig reactions. Michael J. Krische of the University of Texas showed (J. Am. Chem. Soc. 2014, 136, 11902) that Ru-mediated addition of 17 to the aldehyde derived in situ from 16 gave 18 with high Z-selectivity. Vladimir Gevorgyan of the University of Illinois at Chicago constructed (J. Am. Chem. Soc. 2014, 136, 17926) the trisubstituted alkene 20 by the intramolecular Heck cyclization of 19. Kálmán J. Szabó of Stockholm University opti­mized (Chem. Commun. 2014, 50, 9207) the Pd-catalyzed borylation of the alkene 21 followed by in situ addition to the aldehyde 22 to give 23. Boris A. Trofimov of the Irkutsk Institute of Chemistry Siberian Branch devel­oped (Eur. J. Org. Chem. 2014, 4663) aqueous conditions for the preparation of a propargylic alcohol 26 by the addition of an alkyne 25 to the ketone 24. Huanfeng Jiang of the South China University of Technology prepared (Angew. Chem. Int. Ed. 2014, 53, 14485) the alkyne 28 by the oxidative elimination of the tosylhydrazone 27.

Christine L. Willis and Varinder K. Aggarwal at the University of Bristol have developed (Angew. Chem. Int. Ed. 2012, 51, 12444) a procedure for the diastereodivergent synthesis of trisubstituted alkenes via the protodeboronation of allylic boronates, such as in the conversion of 1 to either 2 or 3. An alternative approach to the stereoselective synthesis of trisubstituted alkenes involving the reduction of the allylic C–O bond of cyclic allylic ethers (e.g., 4 to 5) was reported (Chem. Commun. 2012, 48, 7844) by Jon T. Njardarson at the University of Arizona. A novel synthesis of allylamines was developed (J. Am. Chem. Soc. 2012, 134, 20613) by Hanmin Huang at the Chinese Academy of Sciences with the Pd(II)-catalyzed vinylation of styrenes with aminals (e.g. 6 + 7 to 8). Eun Jin Cho at Hanyang University showed (J. Org. Chem. 2012, 77, 11383) that alkenes such as 9 could be trifluoromethylated with iodotrifluoromethane under visible light photoredox catalysis. David A. Nicewicz at the University of North Carolina at Chapel Hill developed (J. Am. Chem. Soc. 2012, 134, 18577) a photoredox procedure for the anti-Markovnikov hydroetherification of alkenols such as 11, using the acridinium salt 12 in the presence of phenylmalononitrile (13). A unique example of “catalysis through temporary intramolecularity” was reported (J. Am. Chem. Soc. 2012, 134, 16571) by André M. Beauchemin at the University of Ottawa with the formaldehyde-catalyzed Cope-type hydroamination of allyl amine 15 to produce the diamine 16. A free radical hydrofluorination of unactivated alkenes, including those bearing complex functionality such as 17, was developed (J. Am. Chem. Soc. 2012, 134, 13588) by Dale L. Boger at Scripps, La Jolla. Jennifer M. Schomaker at the University of Wisconsin at Madison reported (J. Am. Chem. Soc. 2012, 134, 16131) the copper-catalyzed conversion of bromostyrene 19 to 20 in what was termed an activating group recycling strategy. A rhodium complex 23 that incorporates a new chiral cyclopentadienyl ligand was developed (Science 2012, 338, 504) by Nicolai Cramer at the Swiss Federal Institute of Technology in Lausanne and was shown to promote the enantioselective merger of hydroxamic acid derivative 21 and styrene 22 to produce 24.

Kiyotomi Kaneda of Osaka University devised (Angew. Chem. Int. Ed. 2010, 49, 5545) gold nanoparticles that efficiently deoxygenated an epoxide 1 to the alkene 2. Robert G. Bergman of the University of California, Berkeley, and Jonathan A. Ellman, now of Yale University, reported (J. Am. Chem. Soc. 2010, 132, 11408) a related protocol for deoxygenating 1,2-diols. Dennis A. Dougherty of Caltech established (Org. Lett. 2010, 12, 3990) that an acid chloride 3 could be reduced to the phosphonate 4. Pei-Qiang Huang of Xiamen University effected (Synlett 2010, 1829) reduction of an amide 5 by activation with Tf2O followed by reduction with NaBH4. André B. Charette of the Université de Montreal described (J. Am. Chem. Soc. 2010, 132, 12817) parallel results with Tf2O/Et3SiH. David Milstein of the Weizmann Institute of Science devised (J. Am. Chem. Soc. 2010, 132, 16756) a Ru catalyst for the alternative reduction of an amide 7 to the amine 8 and the alcohol 9. Shi-Kai Tian of the University of Science and Technology of China effected (Chem. Commun. 2010, 46, 6180) reduction of a benzylic sulfonamide 10 to the hydrocarbon 11. Thirty years ago, S. Yamamura of Nagoya University reported (Chem. Commun. 1967, 1049) the efficient reduction of a ketone to the corresponding methylene with Zn/HCl. Hirokazu Arimoto of Tohoku University established (Tetrahedron Lett. 2010, 51, 4534) that a modified Zn/TMSCl protocol could be used following ozonolysis to effect conversion of an alkene 12 to the methylene 13. José Barluenga and Carlos Valdés of the Universidad de Oviedo effected (Angew. Chem. Int. Ed. 2010, 49, 4993) reduction of a ketone to the ether 16 by way of the tosylhydrazone 14. Kyoko Nozaki and Makoto Yamashita of the University of Tokyo and Dennis P. Curran of the University of Pittsburgh found (J. Am. Chem. Soc. 2010, 132, 11449) that the hydride 18 (actually a complex dimer) could effect the direct reduction of a halide 17 and also function as the hydrogen atom donor for free radical reduction and as the hydride donor for the Pd-mediated reduction of an aryl halide.

Miquel Costas of the Universitat de Girona developed (J. Am. Chem. Soc. 2013, 135, 14871) an iron catalyst for the enantioselective epoxidation of the Z-ester 1 to 2. Although the α-chloro aldehyde derived from 3 epimerized under the reaction conditions, Robert Britton of Simon Fraser University showed (Org. Lett. 2013, 15, 3554) that the subsequent aldol condensation with 4 favored one enantiomer, leading to 5 in high ee. Other selective aldol condensations of 4 (not illustrated) have been reported by Zorona Ferjancic and Radomir N. Saicic of the University of Belgrade (Eur. J. Org. Chem. 2013, 5555) and by Tomoya Machinami of Meisei University (Synlett 2013, 24, 1501). Motomu Kanai of the University of Tokyo condensed (Org. Lett. 2013, 15, 4130) D-arabinose 6 with diallyl amine and the alkyne 7 to give the amine 8 as a mixture of diastereomers. Naoya Kumagai and Masakatsu Shibasaki of the Institute of Microbial Chemistry combined (Angew. Chem. Int. Ed. 2013, 52, 7310) 9 and 10 to prepare the α-chiral amine 11. Tomoya Miura and Masahiro Murakami of Kyoto University used (J. Am. Chem. Soc. 2013, 135, 11497) an Ir catalyst to migrate the alkene of 13 to the E allyl boro­nate, that then added to 12 to give 14. Gong Chen of Pennsylvania State University alkylated (J. Am. Chem. Soc. 2013, 135, 12135) the β-H of 15 with 16 to give selec­tively the diastereomer 17. Geoffrey W. Coates of Cornell University devised (J. Am. Chem. Soc. 2013, 135, 10930) catalysts for the carbonylation of the epoxide 18 to either regioisomer of the β-lactone 19. Yujiro Hayashi of Tohoku University combined (Chem. Lett. 2013, 42, 1294) the inexpensive succinaldehyde 20 and ethyl glyoxylate 21 to give the versatile aldehyde 22. Nuno Maulide of the Max-Planck-Institut für Kohlenforschung Mülheim effected (J. Am. Chem. Soc. 2013, 135, 14968) Claisen rearrangement of 23 to give, after reduc­tion and hydrolysis, the aldehyde 24. Stephen G. Davies of the University of Oxford reported (Chem. Commun. 2013, 49, 7037) a related Claisen rearrangement (not illustrated). Ying-Chun Chen of Sichuan University devised (Org. Lett. 2013, 15, 4786) the cascade combination of 25 and 26 to give 27.