CHIRAL AZOLE DERIVATIVES .2. SYNTHESIS OF ENANTIOMERICALLY PURE 1-ALKYLIMIDAZOLES

4,5-Dicyanoimidazole has been reacted with racemic and enantiopure alc ohols 7 (entries 1-7 in Table 1) under Mitsunobu conditions to give 1- alkyl-4,5-dicyanoimidazole derivatives 8, which in turn have been tran sformed by hydrolysis and decarboxylation into 1-alkylimidazoles 10 in good overall yield and high enantiomeric excess. In contrast, when ap plied to benzyl and benthydryl alcohols (entries 8-15), this sequence afforded the final compounds in good overall yield, but as racemic mix tures. The 1-(1-phenylalkyl)imidazole derivative (S)-(+)-24 was, howev er, prepared in enantiopure form starting from the corresponding (S)-( -)-alpha-methylbenzylamine (21) using the Marckwald procedure, which e ntailed the alkylation of 21 with bromoacetaldehyde dimethyl acetal, f ollowed by the construction of the imidazole ring through reaction wit h potassium thiocyanate and final Ra-Ni desulfuration. Following the s ame procedure, (S)-(+)-10c was also synthesized, proving the stereoche mical outcome of the Mitsunobu reaction.