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 percent d 4 (using Wilkinson's catalyst, tris (triphenylphosphine)‐chlororhodium) or percent d 2 (using Lindlar's catalyst, Pd on CaCO 3 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 percent d 4 . This scatter was not observed with the corresponding THP ethers.