Diastereoselective addition of organometallic reagents to chiral iminium ions: Synthesis of (S)-(+)-cryptostyline I.

✍ Scribed by Richard P. Polniaszek; Lawrence W. Dillard

• Publisher: Elsevier Science
• Year: 1990
• Tongue: French
• Weight: 271 KB
• Volume: 31
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)94630-6

✦ Synopsis

lminium ion 2c participates in stereoselective nucleophilic addition reactions wkh Grfgnard reagents. Analysis of the products from reaction of 5hexenylmagnesium bromide with iminium ion 2a suggests that these reactions proceed by a polar (two electron) mechanism. The utility of this chemistry is demonstrated in a stereospecifii synthesis of (S)-(+)-cryptostyline I.

We are interested in detetining the factors which influence the sense and extent of stereoselection associated with the addition of various nucleophiles to iminium ions. Previous publications from these laboratories1 have revealed that iminium ions l&c undergo highly stereoselective hydride reduction with NaBH4 in methanol to afford (1 S)-1,2disubstituted-1,2,3,4tetrahydmisoquinolines. This letter describes complementary experiments involving nucleophific addiion of organometalfic reagents to iminium ions 2a-c.