Study and optimisation of an α-selective catalytic allylic benzylborylation using Morita-Baylis-Hillman adducts and organoboron pronucleophiles

Abstract

Asymmetric allylic alkylation (AAA) is a chemical reaction in which an allylic substrate undergoes substitution by a nucleophile in the presence of a chiral catalyst, leading to the stereoselective formation of a new carbon–carbon or carbon–heteroatom bond at the allylic position. AAA reactions have become one of the most powerful and versatile catalytic strategies for the stereoselective formation of such bonds. For several years, these reactions were predominantly catalysed by transition metals. However, from 2000, many fundamental catalytic processes began to be developed under organocatalytic conditions, including the catalytic AAA using Morita-Baylis–Hillman (MBH) adducts as electrophilic substrates. Since then, significant progress has been made in the development of AAA methodologies. However, most reported AAA reactions involving MBH adducts have focused on achieving γ-selective asymmetric alkylation. In contrast, α-alkylations have been less extensively explored. The main goal of this TFG is the study and optimisation of an α-selective asymmetric allylic benzylborylation using MBH fluorides or MBH carbonates and organoboron pronucleophiles activated via desilylation or deborylation. Building on the knowledge previously acquired by the research group to achieve γ-selective asymmetric allylic benzylborylation, the objective of this TFG is to switch this γ-selectivity to α-selectivity. The most innovative aspect of the process is the use of the leaving group (LG) as a catalytic reaction initiator. The homoallylic benzylborylated product obtained is a valuable intermediate due to the versatile reactivity of organoboron compounds, which can serve as building blocks for the synthesis of other complex organic compounds