Synthesis of Enantiopure Homoallylic Alcohols and Ethers by Diastereoselective Allylation of Aldehydes

Enantiopure homoallylic alcohols 5 , which are important building blocks in organic synthesis, are obtained with an ee of greater than 99% and a yield of 75–95% by cleavage of the secondary homoallylic ethers 4 using sodium in liquid ammonia. The ethers 4 are formed with excellent diastereoselectivity and in 52–89% yield by treatment of the aldehydes 1 with the trimethylsilyl ether of N ‐trifluoroacetylnorpseudoephedrine ( 2 ) in the presence of a catalytic amount of TMS triflate or TMS borontriflate, followed by addition of allylsilane 3 . Nearly all achiral aliphatic aldehydes employed gave a diastereoselectivity of over 99:1. With the chiral aldehydes 24 , the difference between matched and mismatched pairs was low; this reveals that there is strong reagent control.