Allylic borylation of tertiary allylic alcohols: a divergent and straightforward access to allylic boronates

Abstract

A facile and divergent synthetic process for converting tertiary allylic alcohols to multiply substituted allylic boronates is reported. This methodology is especially effective for tertiary alcohol substrates, providing the corresponding allylic boronates in moderate to good yields.

Reductive Aromatization of Quinols with B2pin2 as Deoxidizing Agent

“…Based on the aforementioned observations and previous reports, we propose a mechanism shown in Scheme . Non‐halogen‐substituted 1 would undergo borylation on ɑ,β ‐unsaturated carbonyl moiety assisted by neighboring hydroxyl group.…”

“…In case of deoxygenation, borohydride is crucial to drive the cleavage of C−O bond, achieving nucleophilic substitution towards borate ester. Alternatively, deoxygenation process with diboron compounds is also available, requiring anchimeric assistance of alkene to undergo Fernádez‐type diborylation/B−O elimation or via six‐membered ring (followed by protodeboronation sometimes) to complete deoxygenation process (Scheme b) wherein the olefin migration during this transformation is inevitable. Parallelly, Song‐type cascade borylation/B−O elimation from propynols could also afford deoxygenated structures (Scheme c) .…”

Regioselectivity Switch Towards the Development of Innovative Diels‐Alder Cycloaddition and Productive Applications in Organic Synthesis

“…The enantiomerically enriched allylboronates were easily accessed via variety of pathways (general pathway shown in Scheme 7a) [86–90] . Allylic boronates are versatile intermediates in a range of valuable synthetic transformations due to their promising stability and reactivity [91–95] . However, the particular challenge in accomplishing a stereospecific and regioselective cross‐coupling reaction is not only maintaining enantiomeric purity, but also controlling the regiochemical outcomes in the same sequence [96] .…”

Inter‐Element Boration Reactions of Carbon‐Carbon Multiple Bonds via Lewis‐Basic Activation of Boron Reagents

“…Hirano and Uchiyama independently reported the same transformation (Scheme 6). [25] Based on DFT calculations that excluded the possibility of S N 2’‐type allylic boration involving a six‐membered cyclic transition state, they proposed that the product is formed through diboration of the carbon‐carbon double bond [16] followed by boron‐Wittig reaction to remove the oxygen atom. The poor stereoselectivity observed in the case of the allylic alcohol with methyl and tertiary butyl groups supports the view that the boron‐introducing event is not associated with a cyclic transition state.…”