Synthesis of 2-alkyl-2-boryl-substituted-tetrahydrofurans via copper(i)-catalysed borylative cyclization of aliphatic ketones

Abstract

A new method was developed for synthesizing 2-alkyl-2-boryl-tetrahydrofuran derivatives from aliphatic ketones using a copper(i)/N-heterocyclic carbene complex catalyst.

First-Row d-Block Element-Catalyzed Carbon–Boron Bond Formation and Related Processes

“…The migration is probably driven by the formation of a strong B–N bond. Likewise, copper alkoxides, formed upon the addition of boryl-cuprate to carbonyls, are able to undergo intramolecular cyclization with a tethered alkyl halide (Scheme c) . In this particular case, previously inaccessible 2-alkyl-boryl-substituted-tetrahydrofurans are generated.…”

“…Likewise, copper alkoxides, formed upon the addition of boryl-cuprate to carbonyls, are able to undergo intramolecular cyclization with a tethered alkyl halide (Scheme 157c). 588 In this particular case, previously inaccessible 2-alkylboryl-substituted-tetrahydrofurans are generated. Although the copper(I)-catalyzed borylation of aldehydes is well-known, Ito was able to convert the α-hydroxy trifluoroborate intermediates into potassium acyltrifluoroborates (KAT) after an oxidation step (Scheme 157d).…”

Copper-Catalyzed Borylative Difunctionalization of π-Systems

“…In 2019, Ito reported a borylative cyclization of aliphatic ketones using a Cu­(I)/ N -heterocyclic carbene complex catalyst (Scheme ). It should be noted that the diboration of aldehydes and ketones has been previously explored, however the intrinsic lability of the O -bound boronate often leads to the free alcohol. − After addition of the copper–boryl species to ketone 77 , an intramolecular substitution generated 78 in moderate yield. Alkyl chlorides were the least reactive toward competing direct substitution pathways.…”