- Process for the preparation of an oxirane, aziridine or cyclopropane
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A process for the preparation of an oxirane, aziridine or cyclopropane of formula (I), wherein X is oxygen, NR4or CHR5; R1is hydrogen, alkyl, aryl, heteroaromatic, heterocyclic or cycloalkyl; R2is hydrogen, alkyl, aryl, heteroaromatic, CO2R8, CHR14NHR13, heterocyclic or cycloalkyl; or R1and R2join together to form a cycloalkyl ring; R3and R10are, independently, hydrogen, alkyl, aryl, heteroaromatic, CO2R8, R83Sn, CONR8R9, trialkylsilyl or triarylsilyl; R4is an electron withdrawing group; R5is alkyl, cycloalkyl, aryl, heteroaromatic, SO2R8, SO3R8, COR8, CO2R8, CONR8R9, PO(R8)2, PO(OR8)2or CN; R8and R9are independently alkyl or aryl; and R13and R14are independently hydrogen, alkyl or aryl is provided. The process comprises degrading a compound of formula (II), (IIa), (IIb) or (IIc): wherein R3and R10are as defined above; Y is a cation; depending on the nature of Y, r is 1 or 2; and L is a suitable leaving group, to form a diazo compound. The diazo compound is reacted with a suitable transition metal catalyst, and the product thereof reacted with a sulphide of formula SR6R7, wherein R6and R7are independently alkyl, aryl or heteroaromatic, or R6and R7join together to form an optionally substituted ring which optionally includes an additional heteroatom. This product is then reacted with an aldehyde, ketone, imine or alkene.
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- Synthesis and Crystal Structure of a Novel Camphor Based Thioaceal
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The synthesis of the very first example of a thioacetal containing two camphor skeletons is described. The acetal was prepared by treating 10-mercapto-iso-borneol with camphorquinone and its stereochemistry confirmed by NMR spectroscopy and X-ray crystallography.
- Ravindran, Swarnam S,Skiti, Neliswa,McCleland, Cedric,Barton, Benita,Bacsa, John
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p. 1056 - 1069
(2007/10/03)
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- Stereoselective synthesis of δ-lactones from 5-oxoalkanals via one-pot sequential acetalization, tishchenko reaction, and lactonization by cooperative catalysis of samarium ion and mercaptan
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By the synergistic catalysis of samarium ion and mercaptan, a series of 5-oxoalkanals was converted to (substituted) δ-lactones in efficient and stereoselective manners. This one-pot procedure comprises a sequence of acetalization, Tishchenko reaction and lactonization. The deliberative use of mercaptan, by comparison with alcohol, is advantageous to facilitate the catalytic cycle. The reaction mechanism and stereochemistry are proposed and supported by some experimental evidence. Such samarium ion/mercaptan cocatalyzed reactions show the feature of remote control, which is applicable to the asymmetric synthesis of optically active δ-lactones. This study also demonstrates the synthesis of two insect pheromones, (2S,5R)-2-methylhexanolide and (R)-hexadecanolide, as examples of a new protocol for asymmetric reduction of long-chain aliphatic ketones.
- Hsu,Fang
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p. 8573 - 8584
(2007/10/03)
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- The Use of Chiral Sulfides in Catalytic Asymmetric Epoxidation
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Non racemic epoxides with ee's of 23-41percent have been prepared from aldehydes and phenyl diazomethane using catalytic amounts of sulfides derived from camphor.
- Aggarwal, Varinder K.,Thompson, Alison,Jones, Ray V. H.,Standen, Mike
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p. 2557 - 2564
(2007/10/03)
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- A New Resolution Procedure for the Preparation of Both (R)-(+)- and (S)-(-)-4-tert-Butoxycyclopent-2-enone from Racemic 4-tert-Butoxycyclopent-2-enone and Conversion of (R)-(+)-Butoxycyclopent-2-enone into (R)-(+)-4-Acetoxycyclopent-2-enone. A New Method for the Determination of the ...
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(1S)-(-)-10-Mercaptoisoborneol undergoes conjugate addition to (+/-)-4-tert-butoxycyclopent-2-enone in methanol containing N,N,N',N'-tetramethylethylenediamine to give a 1:1 mixture of diastereomers of 3-tert-butoxy-4-heptanyl)methyl>thio>cyclopentanone in 93-95percent yield.The mixture is converted by m-chloroperbenzoic acid into the corresponding sulfoxide mixture.The (3R,4R,RS)-sulfoxide isomer, whose absolute configuration has been determined by X-ray crystallography, crystallizes cleanly from this mixture in an enantiomeric yield of 76percent from the corresponding sulfide.It is decomposed on silica gel to generate (R)-(+)-4-tert-butoxycyclopent-2-enone, with an enantiomeric purity of >/- 99.9percent in 92percent yield from the sulfoxide, and 10-thiodiisobornyl 10'-sulfoxide.Similarly, the (S)-(-)-enone is prepared from (1R)-(+)-10-mercaptoisoborneol.The (+/-) and the (R)-(+)-enone, respectively, are converted by a catalytic amount of FeCl3 in acetic anhydride into (+/-) and (R)-(+)-4-acetoxycyclopent-2-enone (with an enantiomeric purity of >/- 99.9percent) in 80percent yield.The enantiomeric purity of the products was assessed through their treatment with (-)-10-mercaptoisoborneol and analysis of the adducts by HPLC and 400-MHz 1H NMR spectroscopy.
- Eschler, Bart M.,Haynes, Richard K.,Ironside, Michael D.,Kremmydas, Steve,Ridley, Damon D.,Hambley, Trevor W.
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p. 4760 - 4766
(2007/10/02)
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- Self-Induced Diastereoselective Oxidation of Vinyl Sulfides Bearing a Chiral Hydroxy Group as a Way of Preparation of Optically Active Sulfinyl Dienophiles and Their Use in the Asymmetric Diels-Alder Reaction to Cyclopentadiene
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Dienophiles 4,5,4' and 5' add with excellent diastereoselectivity to cyclopentadiene as a result of the fact that they assembled most features that are known to govern facial selectivity.Their synthesis entails stereoselective Michael addition of hydroxyt
- Lucchi, Ottorino De,Lucchini, Vittorio,Marchioro, Carla,Valle, Giovanni,Modena, Giorgio
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p. 1457 - 1466
(2007/10/02)
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- Asymmetric Diels-Alder Reactions of Sulphinyl-activated Dienophiles obtained via a Self-induced Chiral Oxidation
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The Diels-Alder cycloaddition of activated vinyl sulphoxides (1), that are readily obtained by a self-induced chiral oxidation, proceeds highly diastereoselectively to form the corresponding cycloadducts (4) that can be converted into 2-substituted norbor
- Lucchi, Ottorino De,Marchioro, Carla,Valle, Giovanni,Modena, Giorgio
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p. 878 - 880
(2007/10/02)
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