2.

Improved preparation of halopropyl bridged carboxylic ortho esters

Richard J. Petroski,

Org. Commun. (2008), 1:3 ; 48-53

USDA, Agricultural Research Service, National Center for Agricultural Utilization Research,

Crop Bioprotection Research Unit, 1815 N. University Street, Peoria , Illinois 61604

Abstract: Bridged ortho esters of 3-halopropyl carboxylic acids were prepared by esterification of 3-methyl-3-hydroxymethyloxetane with 3-bromopropionyl chloride and pyridine in dry THF, followed by rearrangement with boron trifluoroetherate, to afford 1-(2-bromoethyl)-4-methyl-2,6,7-trioxabicyclo[2,2,2]-octane. The 1-(2-iodoethyl)-4-methyl-2,6,7-trioxabicyclo[2,2,2]-octane analogue could not be prepared directly by halogen exchange of 1-(2-bromoethyl)-4-methyl-2,6,7-trioxabicyclo[2,2,2]-octane but could be prepared by halogen exchange of the (3-methyloxetan-3-yl)methyl 3-bromopropanoate with a mixture of sodium iodide and anhydrous sodium sulfate in acetone, followed by rearrangement with boron trifluoroetherate.

Keywords: bridged carboxylic ortho esters, 1-(2-bromoethyl)-4-methyl-2,6,7-trioxabicyclo[2,2,2]-octane, 1-(2-iodoethyl)-4-methyl-2,6,7-trioxabicyclo[2,2,2]-octane, protected 3-halopropionic acid