Coupling Reactions on Secondary Allylic, Propargylic, and Alkyl Carbons Using Organoborates/Ni and RMgX/Cu Reagents

Abstract

In the first part of this review, secondary carbon-carbon bond formation by using allylic coupling reactions with aryl and alkenyl borates is presented. Early investigations have revealed the suitability of a nickel catalyst and [RTB(OMe)3]Li (RT: transferable group). Due to their low reactivity, the borates were converted to more reactive congeners possessing an alkanediol ligand, such as 2,3-butanediol and 2,2-dimethyl-1,3-propanediol. Borates with such diol ligands were used to install aryl and alkenyl groups on the monoacetate of 4-cyclopentenyl-1,3-diol. Furthermore, alkenyl borates showed sufficient reactivity toward less reactive allylic alcohol derivatives with bromine atoms at the cis position, producing dieneyl alcohols. In the second part, copper-based and/or copper-catalyzed substitutions of secondary allylic picolinates, propargylic phosphonates, and alkyl (2-pyridine)sulfonates with RMgX are briefly summarized. The application of these reactions to the synthesis of biologically active compounds is also discussed.

Keywords

• borate
• boronate ester
• nickel
• secondary carbon
• coupling
• substitution