Borane-Catalysed Hydroboration of Alkynes and Alkenes

Abstract

Simple, commercially available borane adducts, H3B·THF and H3B·SMe2, have been used to catalyse the hydroboration of alkynes and alkenes with pinacolborane to give the alkenyl and alkyl boronic esters, respectively. Alkynes and terminal alkenes underwent highly regioselective hydroboration to give the linear boronic ester products. Good functional group tolerance was observed for substrates bearing ester, amine, ether and halide substituents. This catalytic process shows comparable reactivity to transition-metal-catalysed hydroboration protocols.

Aluminum-Catalyzed Hydroboration of Alkenes

“…Presumably, in situ conversion to the AlH 3 by reaction with HBpin, proceeds during catalysis. Inspired by the recent reports of nucleophileinitiated hydroboration reactions 17,18 we decided to investigate other metal hydrides under our reaction conditions. Although both LiH and NaH were active catalysts, the decreased yields using these hydride reagents suggests a catalytic role for aluminum beyond simple hydride delivery.…”

Lithium diamidodihydridoaluminates: bimetallic cooperativity in catalytic hydroboration and metallation applications

“…11 It is significant that to date most Al-based catalysts for such hydroboration reactions involve neutral complexes. Given our interest in bimetallic systems that can function synergistically under stoichiometric regimes, 12 and recent advances suggesting that borates are crucial reaction intermediates in hydroboration, 13,14 we propose that aluminates would exhibit even greater reactivity. In this contribution we introduce anionic complexes to this important emerging area through a series of heteroleptic lithium diamidodihydridoaluminate complexes with the bulky 1,1,1,3,3,3hexamethyldisilazide ligand [HMDS, (Me 3 Si) 2 N À ].…”

Synform Issue 2018/10

“…Neither Barbier, nor Sabatier's collaborator Jean Baptiste Senderens, received the prize, despite their contribu tions being essentially of equal importance with those of the laureates. This omission was an injustice noted by Grignard himself, 11 who wrote to his friend Meunier on November 13, 1912 (just days after his Nobel was announced) "…to tell the truth, and between us, I would even have preferred to wait a little longer, to see the prize shared between Sabatier and Senderens and then share it myself with Barbier at a later time, But what can I do against such a verdict if not congra tulate myself for it! You will be very kind to give me as much information as you can on the state of health and on the state of mind of Barbier.…”

“…[6][7][8][9] This is also true of our work on main group catalysis where understand ing the mechanism of catalysis has opened exciting new areas of research. 10,11 We have been very fortunate to work with a number of exceptional academic and industrial collaborators.…”