Studies on a catalytic version of the Matteson asymmetric homologation reaction.

Keith Smith,Mohammed B Alshammari,Basil A Saleh,Mark C Elliott,Gamal A El-Hiti

doi:10.1039/d1ob00604e

Abstract

Studies of a catalytic asymmetric version of the Matteson reaction between dichloromethylboronates and organolithium reagents have been undertaken. From several different chiral catalytic systems studied, only one based on a mannitol derivative has given substantial asymmetric induction close to that previously achieved with a bis(oxazoline) derivative and ytterbium triflate. More detailed study of the latter reaction revealed that fresh ytterbium triflate actually reduced the level of asymmetric induction, while "aged" ytterbium triflate, or a fresh sample that had been treated with water, brought about improved induction. The implications of these findings are discussed.

Highlights

Boronic acid derivatives are important intermediates with potential applications in areas such as medicine and organic synthesis,[1] while the use of chiral catalysts has proven to be efficient for the asymmetric synthesis of various organic compounds.[2,3,4,5,6] Boronic esters are generally stable compounds with low to moderate toxicity and have been widely used in the production of either carbon–carbon or carbon-heteroatom bonds.[7]
From several different chiral catalytic systems studied, only one based on a mannitol derivative has given substantial asymmetric induction close to that previously achieved with a bis(oxazoline) derivative and ytterbium triflate
The synthesis of various alkylboronates should be easier than synthesis of dichloromethylboronate and a range of alkyllithiums

Summary

Introduction

Boronic acid derivatives are important intermediates with potential applications in areas such as medicine and organic synthesis,[1] while the use of chiral catalysts has proven to be efficient for the asymmetric synthesis of various organic compounds.[2,3,4,5,6] Boronic esters are generally stable compounds with low to moderate toxicity and have been widely used in the production of either carbon–carbon or carbon-heteroatom bonds.[7]. Aggarwal has made extensive and elegant use of reactions of chiral lithiated alkylcarbamates with B-alkyl pinacolboronates[17,18,19] and such reactions are more widely applicable to synthesis of tertiary alcohols and even to generation of quaternary stereogenic centres.[20] Blakemore’s approach has been to generate labile chiral main group metal carbenoids, such as α-chloroalkyllithiums in situ.[21,22,23] These approaches are undoubtedly valuable additions to the synthetic toolbox, as with the Matteson approach they require a stoichiometric amount of the chiral auxiliary, and it would be desirable to be able to introduce the chiral control through a catalytic agent.

Results and discussion

Conclusions

Boronic Acids