For the first time have boron-containing weak Lewis acids been demonstrated to be active components of Frustrated Lewis Pair (FLP) catalysts in the hydrogenation of ketones to alcohols. Combining the organosuperbase (pyrr) P=NtBu with the Lewis acid 9-(4-CF -C H )-BBN generated an "inverse" FLP catalyst capable of hydrogenating a range of aliphatic and aromatic ketones including N-, O- and S-functionalized substrates and bio-mass derived ethyl levulinate. Initial computational and experimental studies indicate the mechanism of catalytic hydrogenation with "inverse" FLPs to be different from conventional FLP catalysts that contain strong Lewis acids such as B(C F ) .

The phosphoranylideneketenes R3PCCO (R = phenyl, cyclohexyl) and their Lewis acid base adducts were synthesized and structurally as well as spectroscopically characterized.

Stoichiometric and catalytic reactions of terminal alkynes with various FLPs and Lewis acid–base adducts have been investigated. Reactions of phenylacetylene with FLPs composed of the Verkade base N­[CH2CH2NPri]3P (1) and the Lewis acids BPh3, 9-hexyl-BBN, and 9-BBN gave [N­(CH2CH2NPri)3PH]­[PhCC-BPh3] (2), [N­(CH2CH2NPri)3PH]­[9-hexyl-9-PhCC-BBN] (3), and [N­(CH2CH2NPri)3PH]­[9-PhCHCH-9-PhCC-BBN] (4). The binuclear Lewis acid–base adduct (C6F5)3Al–N­[CH2CH2NPri]3P–Al­(C6F5)3 (6) effectively catalyzed the dimerization of terminal alkynes to gem-1,3-enynes.

A method for the generation of 5-isoxazolidinones with exocyclic phosphonium ylide functionalities via [2+3] cycloaddition of Ph3PCCO and aldonitrones has been developed and applied in the synthesis of 4-alkylidene-5-isoxazolidinones via Wittig olefination. The reaction proceeds by BPh3 catalysis under mild conditions and with a broad substrate scope. A reaction pathway involving the activation of the aldonitrone via interactions with the Lewis acid BPh3 is proposed.

Dedicated to Dr. Doug Stephan in honour of his 70 th birthdayThe reactivity of alkynylphosphines with Lewis acidic boranes has been well established in recent years thanks to the advent of frustrated Lewis pairs (FLPs), often leading to a 1,1carboboration reaction and the formation of an intramolecular phosphinoborane FLP. Our group recently discovered that introduction of an ionizable group in the γ-position of an alkynylphosphine result in an unexpected rearrangement reaction to yield zwitterionic allenic-phosphonium borate products which are produced via a transient 3-coordinate phosphonium allenylidene. Herein, we describe how substituent effects on the γ-carbon impact this reactivity and explore how bis(alkynyl)phosphines behave under similar reaction conditions.