Patent ID: 7081537

Claim:
A process for preparing compounds of the general formula (2) where X is S or O and R 1 is selected from the group consisting of hydrogen, metals of the first or second main group, linear or branched C 1 –C 12 -alkyl, C 6 –C 15 -aryl or C 7 –C 21 -aralkyl radicals, dialkylsilyl and trialkylsilyl, dialkylarylsilyl, diarylalkylsilyl, triarylsilyl radicals, and the organic radicals of the silyl radicals are in turn selected from C 1 –C 12 -alkyl and C 6 –C 15 -aryl radicals and R 2 is selected from the group consisting of linear or branched C 1 –C 12 -alkyl, C 6 –C 15 -aryl and C 7 –C 21 -aralkyl radicals and P is an amino protecting group and E is a radical selected from the group consisting of optionally halogen, cyano, nitro or ester group-substituted, linear or branched C 1 –C 12 -alkyl, C 3 –C 10 -alkenyl, C 6 –C 15 -aryl and C 7 –C 21 -aralkyl radicals, or is an acyl or formyl group, comprising adding a base to a reaction mixture comprising a compound of the general formula (1) and an electrophile E-Y where Y is a leaving group, and carrying out the reaction at a temperature of greater than −40° C.