A highly diastereoselective synthesis of (E)-B-2-(1-cyclopropyl-1-alkenyl)-1,3,2-dioxaborinanes. Isolation and oxidation to alkyl cyclopropyl ketones

✍ Scribed by Narayan G. Bhat; Laura Garcia; Victoriano Tamez Jr.

• Publisher: Elsevier Science
• Year: 2003
• Tongue: French
• Weight: 98 KB
• Volume: 44
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(03)01841-0

✦ Synopsis

A convenient, novel synthesis of alkyl cyclopropyl ketones based on Z-1-bromo-1-alkenylboronate esters is developed. a-Bromo-(Z)-1-alkenylboronate esters readily available from literature procedures smoothly undergo a reaction with cyclopropylmagnesium bromide in tetrahydrofuran to provide the corresponding 'ate' complexes. These 'ate' complexes undergo intramolecular nucleophilic substitution reactions to provide the corresponding (E)-1-alkenylboronate esters containing cylcopropyl moiety for the first time in good isolated yields (68-82%). The carbon skeleton present in these intermediates is confirmed by oxidation with hydrogen peroxide and sodium acetate to afford the corresponding alkyl cyclopropyl ketones in good yields (72-85%).