(1-Methoxyvinyl)boronic and (1-chlorovinyl)boronic esters

✍ Scribed by Donald S. Matteson; Ellen C. Beedle

• Book ID: 102846395
• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 542 KB
• Volume: 1
• Category: Article
• ISSN: 1042-7163
• DOI: 10.1002/hc.520010203

✦ Synopsis

s)-Pinanediol ( I -methoxyvinyl)boronate (1) was prepared from ( I -methoxyvinyl)-lithium and triisopropyl borate followed by (s)-pinanediol. Attempted reaction with (dichloromethy1)lithium failed, and reaction with butylmagnesium chloride followed by acetic acid yielded a mixture of diastereomers of (s)-pinanediol ( I -methoxy-1-methyl-penty1)boronate (2). (s)-Pinanediol ( I -chlorovinyl)boronate (4) has been prepared by dehydrochlorination of (s)-pinanediol I ,I -dichloroethylboronate (3) with lithium chloride in dimethylfomamide. Reaction of 4 with (dichbro-methy1)lithium yielded (s)-pinanediol (lS)-(l,2-di-chloroa1lyl)boronate (5) in 92% diastereomeric excess. Reaction of 5 with RMgX resulted i n a 3 : 1 ratio of displacement of the 1-CI from carbon by R to displacement of the entire 1,2-dichloroallyl group from boron by R. With lithium benzyl oxide, displacement of the 1 -CI from 5 failed entirely. Reaction of 4 with (dibromomethy1)lithium was ineficient and yielded a gross mixture of diastereomers.