Chiral acetals derived from aldehydes and (-)-(2R,4R)-2,4-pentanediol are cleaved selectively by organoaluminumreagents. The reaction proceeds via the retentive-alkylation process with >95% selectivities in most cases. Trialkylaluminum reagent is utilized for higher alkyl transfers, but for smaller alkyl transfers, a newreagent system, combining trialkylaluminum and the halophenols such as pentafluorophenol
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.
2-position of the oxetanes is lost during the reactions suggesting the involvement of a radical process. A novel process for the reductive magnesiation of 2-substituted oxetanes and the metalative cyclization of ω-alkynyl oxetanes is developed using n-propylmagnesium chloride in the presence of an iron catalyst. The generated intermediate organomagnesium compounds react with electrophiles. The reactions of