Acyclic stereoselection. 8. A new class of reagents for the highly stereoselective preparation of threo-2-alkyl-3-hydroxycarboxylic acids by the aldol condensation
Herein, we report a double deprotonation method used for the preparation of ynolates starting from nonbrominated 2,6-di-tert-butylphenyl esters. The current method is superior to the previously described double lithium/halogen exchange approach because easily accessible starting materials are used. This method will be especially useful for preparation of ynolates bearing functional groups in organic
作者:Clayton H. Heathcock、Michael C. Pirrung、Stephen H. Montgomery、John Lampe
DOI:10.1016/s0040-4020(01)93284-3
日期:——
Li enolates of hindered aryl esters condense with aldehydes to give predominantly threo aldols. The method has been explored with esters 3 (DMP propionate), 4 (BHT propionate), and 5 (DBHA propionate). DMP propionate reacts with benzaldehyde and α-unbranched aliphatic aldehydes to give threo:erythro ratios of about 6.5:1. However, with α-branched aliphatic aldehydes, ester 3 gives only threo-aldols.
The stereoselective synthesis of oxetanes; exploration of a new, Mitsunobu-style procedure for the cyclisation of 1,3-diols
作者:Martin Christlieb、John E. Davies、Jason Eames、Richard Hooley、Stuart Warren
DOI:10.1039/b106851b
日期:2001.11.15
A solution of 2-methyl-3-[1-(phenylsulfanyl)cyclohexyl]propane-1,3-diol 1 in toluene treated with triphenylphosphine, Ziram®
2 and DEAD, gave 3-methyl-2-[1-(phenylsulfanyl)cyclohexyl]oxetane 3 in 85% yield. A mechanistic study has been undertaken, optimal conditions have been found and the range of substrates for which the reaction is useful has been explored. We include the results of an X-ray study which shows that compound 33 (the oxidation product of diol 1) is a sulfone rather than a sulfoxide as previously reported.
Access to -2,5-disubstituted iodovinyltetrahydrofurans via the cyclization of γ-silyloxyallenes using n-iodosuccinimide
作者:Robert D Walkup、Lufeng Guan、Sang Woong Kim、Young Soo Kim
DOI:10.1016/0040-4039(92)88075-g
日期:1992.7
Treatment of gamma-(tert-butyldimethylsiloxy)- or gamma-(trimethylsiloxy)allenes bearing various groups at the ether carbon with N-iodosuccinimide resulted in the formation of iodocyclization products, 1-iodo-1-(tetrahydrofuran-2'-yl)ethenes, in good yields and with high selectivity for the cis diastereomer.
(2SR,3SR)-2,4-DIMETHYL-3-HYDROXYPENTANOIC ACID
作者:Montgomery, Stephen H.、Pirrung, Michael C.、Heathcock, Clayton H.