Abstract
A mild gold-catalyzed protodeboronation reaction, which does not require acid or base additives and can be carried out in "green" solvents, is described. As a result, the reaction is very functional-group-tolerant, even to acid- and base-sensitive functional groups, and should allow for the boronic acid group to be used as an effective traceless directing or blocking group. The reaction has also been extended to deuterodeboronations for regiospecific ipso-deuterations of aryls and heteroaryls from the corresponding organoboronic acid. Based on density functional theory calculations, a mechanism is proposed that involves nucleophilic attack of water at boron followed by rate-limiting B-C bond cleavage and facile protonolysis of a Au-σ-phenyl intermediate.
Highlights
Arylboronic acids are readily available and widely used substrates in organic chemistry.[1]
Cheon and co-workers have demonstrated the utility of protodeboronations as a means of removing boronic acid groups after it has been used as a blocking or directing group (Scheme 1).[5]
Our group has investigated many gold-catalyzed reactions using cyclopropenes[16] and allylic alcohols[17] as substrates. As part of these investigations, we explored the use of arylboronic acids as nucleophiles[18] in the gold(I)-catalyzed reaction with allylic[19] alcohols (Scheme 2) and cyclopropenes (Scheme 3)
Summary
Arylboronic acids are readily available and widely used substrates in organic chemistry.[1]. In terms of transitionmetal-catalyzed protodeboronations, previously reported Cu-,7 Ag-,8 or Pd-catalyzed[9] methods typically require the addition of a stoichiometric base and can suffer from selectivity issues, such as coupling or dehalogenation products observed with the Pdcatalyzed method.[9] a mild and more general procedure, which is tolerant of both electron-donating and electron-withdrawing as well as various sensitive functional groups, is required in order to fully harness the potential of boronic acids as traceless blocking and directing groups. We present a mild gold-catalyzed protodeboronation method, which is tolerant of various acid- and base-sensitive groups and can be carried out in “green”, environmentally benign, industrial-friendly solvents such as dimethylcarbonate.[10] the procedure can be adapted to effect deuterodeboronations, which constitutes a practical and regiospecific ipso-deuteration technique. Synthetic methods toward deuterated compounds are regularly applied toward the tritium analogues, which are often used as radiotracers in the pharmaceutical industry.[11]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
