The reaction of cyclic orthoesters of cyclohexanes and steroides with trimethylsilylchloride,-azide and-cyanide points out novel, mechanistic aspects as well as remarkable preparative possibilities. The mixture1 a/1 bof theexo/endostereoisomers of the cyclic orthoesters derived fromcis-cyclohexane-1,2-diol was transformed to the expected 1-yl-ethanoate3of thetrans-2-chlorocyclohexan-1-ol. In contrast the reaction of1 a/1 bwith trimethylsilylazide and trimethylsilycyanide yields the correspondingexo/endomixtures of2 a/2 band2 c/2 dresp. The cyclic orthoester oftrans-cyclohexan-1,2-diol (4) similarily affords the products5 aand5 b, whereas transformation with trimethylsilylchloride 1-yl-ethanoate of thecis-2-chlorocyclohexan-1-ol could not be achieved for steric reasons. The cyclic orthoesters6 a/6 bofcis-cyclohex-1-en-3,4-diol are converted regio- and stereospecifically to the products7and9using trimethylsilychloride and- azide, whereas theexo/endomixture8 a/8 bof the corresponding cyclic orthoester derivative is formed with trimethylsilylcyanide. The orthoesters10 a/10 bprepared from 2,3-cis-dihydroxycyclohexanone-1 give thetrans-2-chloro-3-oxocyclohexyl-ethanoate (11) and its elimination product12. In analogy13is produced by treating10 a/10 bwith trimethylsilylacetate. Theexo/endomixture of cyclic esters14 a/14 b3α-cholestan-2α,3α-diol gives the corresponding mixture15 a/15 bwhen treated with trimethylsilycyanide. Reaction of Trimethylsilychloride with14 a/14 baffords mainly thetrans-diequatorial product17 aand only small amounts of thetrans-diaxial product17b. In contrast the mixture18a/18byields exclusively thetrans-diaxials product20on reaction with trimethylsilylchloride. With trimethylsilcyanide the cyclic orthoester derivative21 a/21 bis formed. The cyclic esters22 a/22 bof 1α,2α-dihydroxychloestanone-3 react with trimethylsilylchloride to give the easily explicable elimination product23and the rearranged 3-methoxy-cholesten-3-one-2 (24). The corresponding cyclic orthesters25 a/25 bof 1α,2α-dihydroxy-3-oxo-androstans-17β-yl-ethanoate in a similar way afford the elimination product26to a small extent and the rearranged 3-methoxy-2-oxo-androstan-17β-yl-ethanoate (27) as the main
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