A Novel Synthesis of (E)-gem-Dimetalloalkenes Containing Boron and Silicon: An Easy Access to Alkyl Trimethylsilyl Ketones

Abstract

A simple, novel synthesis of (E)-gem-dimetalloalkenes containing boron and silicon based on (Z)-1-bromo-1-alkenyl­boronate esters is developed. 1-Bromo-(Z)-1-alkenylboronate esters readily available from literature procedures smoothly undergo a ­reaction with trimethylsilyllithium (easily generated from hexamethyldisilane with methyllithium in hexamethylphosphoramide) to provide the corresponding ‘ate’ complexes. These ‘ate’ complexes undergo intramolecular nucleophilic substitution reaction to provide the corresponding (E)-1-alkenylboronate esters containing trimethylsilyl moiety in good isolated yields (72-85%). The carbon skeletons present in these intermediates are confirmed by oxidation to the corresponding alkyl trimethylsilyl ketones with sodium ­acetate and hydrogen peroxide.

Key words

gem-dimetalloalkenes - trimethylsilyllithium - hexamethyldisilane - alkenylboronate - methyllithium

References

• 1 Brown HC. Bhat NG. Somayaji V. Organometallics  1983,  2:  1311 
• 2 Matteson DS. Majumdar D. Organometallics  1983,  2:  1529 ; and references cited therein
• 3 Tsai DJS. Jesthi PK. Matteson DS. Organometallics  1983,  2:  1543 
• 4 Brown HC. De Lue NR. Yamamoto Y. Maruyama K. Kasahara T. Murahashi S. Sonoda A. J. Org. Chem.  1977,  42:  4088 
• 5 Rathke MW. Chao E. Wu G. J. Organomet. Chem.  1976,  122:  145 
• 6 Brown HC. Imai T. Organometallics  1984,  3:  1293 
• 7 Brown HC. Imai T. Bhat NG. J. Org. Chem.  1986,  51:  5277 
• 8 Brown HC. Soundararajan R. Tetrahedron Lett.  1994,  35:  6963 
• 9 Bhat NG. Martinez C. De Los Santos J. Tetrahedron Lett.  2000,  41:  6541 
• 10 Still WC. J. Org. Chem.  1976,  41:  3063