The sp3-Carbon-Attached Trimethylsilyl Group as Removable Asymmetry-Inducing Auxiliary. 1. Aromatic Resin Acid Ring Systems

Article abstract of DOI:10.1021/jo00193a029

The use of the trimethylsilyl (Me3Si) unit as detachable diastereoselectivity-inducing auxiliary during cationic polycyclization reactions has been examined.Model studies show 2a,b to be easily cyclized to 3a-c in CF3COOH-containing CH2Cl2.Polycyclization of 5a, on treatment with SnCl4 in CH2Cl2, gives a 85:15 ratio of 6a/7a.The same conditions transform 5b into 5percent of 100percent diastereoselectively ortho-cyclized 6b and 46percent of para-cyclized 6c/7c, occurring as a 77:23 epimeric mixture.Desilylation of the cyclized materials, using KO-t-Bu/Me2SO, provides 4a-c and 8a,c.