Organic Chemistry, Short talk
OC-027

Polar Opposites in Phosphorus Catalysis: Applications of 1,3,2-Diazaphospholenes

J. Reed1, N. Cramer1*
1Laboratory of Asymmetric Catalysis and Synthesis, EPF Lausanne

Phosphorus based catalysts have, in recent years, received considerable attention from the synthetic organic chemistry community as a result of their unique and interesting reactivity, and their superior economic and ecological profiles when compared to transition-metal based catalysts. 1,3,2-Diazaphospholenes (DAPs) are a particular class of catalysts that offer orthogonal reactivity to more canonical phosphorus based catalysts (Figure 1).[1] The significant delocalisation of electrons around the heterocyclic core leads an Umpolung of the P-H bond, resulting in the most powerful hydride donor quantified on the Mayr nucleophilicity scale.[2]

We have exploited this remarkable property of the DAPs to develop a range of catalytic reductive methodologies: a bespoke chiral DAP enabled the highly enantioselective conjugate reduction of a wide variety of α,β-unsaturated carbonyl compounds (Figure 2),[3] while the transient phosphorus enolate that is generated in this process could be exploited to generate C-C bonds through a [3,3]-sigmatropic rearrangement.[4] Examination of the solid-state single crystal X-ray diffraction analysis in combination with detailed NMR studies have shed light on mechanism by which these catalysts operate, as well as providing a blueprint for future developments in this field.

[1] Dietrich Gudat,  Asadolla Haghverdi, Martin Nieger, Angew. Chem. Int. Ed. 2000, 39, 3084–3086.
[2] Jingjing Zhang, Jin-Dong Yang, Jin-Pei Cheng, Angew. Chem. Int. Ed. 2019, 58, 5983–5987.
[3] Solène Miaskiewicz*, John H. Reed*, Pavel A. Donets, Caio C. Oliveira, Nicolai Cramer, Angew. Chem. Int. Ed. 2018, 57, 4039–4042.
[4] John H. Reed, Pavel A. Donets, Solène Miaskiewicz, Nicolai Cramer, Angew. Chem. Int. Ed. 2019, 58, 8893-8897.