Catalytic deuteration of alkynols and their tetrahydropyranyl ethers

To ascertain the effect of a replaceable hydrogen on deuterium incorporation, 2‐pentynol, 2‐hexynol, 3‐hexynol, their tetrahydropyranyl (THP) ethers, and the mono‐ and di‐THP ethers of 3‐hexyne‐1,6‐diol were deuterated catalytically with deuterium gas. The differences in percentd4 (using Wilkinson's catalyst,tris(triphenylphosphine)‐chlororhodium) or percentd2 (using Lindlar's catalyst, Pd on CaCO3 poisoned with a lead salt) measured for the alcohols and their THP ethers were, in general, less than 4% with either catalyst. Noticeable exceptions occurred during the deuteration over Wilkinson's catalyst of 2‐pentynol and 2‐hexynol; extensive scatter resulted in a substantial decrease in percentd4. This scatter was not observed with the corresponding THP ethers.