MITSUNOBU REACTION OF UNBIASED CYCLIC ALLYLIC ALCOHOLS

The stereochemical inversion of unbiased allylic alcohols using triphe nylphosphine, diethyl azodicarboxylate, and benzoic acid, commonly kno wn as the Mitsunobu reaction, was studied in three different solvents with specific attention toward the product composition The results gen erated for the Mitsunobu reaction of (R)-3-deuterio-2-cyclohexen-1-ol aad the cis and trans isomers of 1-deuterio-5-methyl-2-cyclohexen-1-ol , 1-deuterio-5-tert-butyl-2-cyclohexen-1-ol, and optically active cia and trans 5-isopropyl-2-methyl-2-cyclohexen-1-ol all gave similar prod uct distributions with respect to inversion rind retention at the carb inol center as well-as sym and anti S(N)2' type addition when THF or b enzene was used as the solvent (CH2Cl2 gave less selective product dis tributions), Interestingly, it was found that the quasi-equatorial and quasi-axial nature of the starting allylic alcohol does not appear to affect the product distribution for this reaction, nor does methyl su bstitution at the central carbon of the allylic alcohol. Sn all cases, significant amounts (8-28%) of non-S(N)2 type products were detected for these sterically unbiased allylic alcohols only 72-77% of the prod uce was from S(N)2 type reaction when sterically undemanding (R)-3-deu terio-2-cyclohexen-1-ol was subjected to Mitsunobu conditions.