Additions of enantioenriched allenylzinc and indium reagents to lactic aldehyde ethers

Allenylzinc and indium reagents were generated in situ through Pd(0)-catalyzed metalation of (R)- and (S)-3-butyn-2-ol-methanesulfonate with Et2Zn ana InI. These reagents add to the benzyl and TBS ethers of(S)-lactic aldehyde to afford diastereomeric stereotriads in;moderate to high yield. The (S)/(S) combination afforded the anti,anti adducts with 94:6-100:0 diastereoselectivity. The (R)I(S) combination was mismatched, affording a mixture of anti,syn and syn,anti adducts in; diastereomeric ratios of ca. 80:20-85:15. Addition of the racemic allenylmetal reagents to the (S)lactic aldehyde ethers afforded the products of matched and mismatched pairings in equal amount.