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2.11.3.2.2.1 Using a Thiourea–Schiff Base Catalyst

DOI: 10.1055/sos-SD-202-00255

Bergin, E.Science of Synthesis: Stereoselective Synthesis, (20112578.

Thiourea 70 has been successfully applied to the hydrophosphonylation of imines to α-aminophosphonates 71 and is the first truly general catalyst for this reaction (Scheme 39).[‌70‌] Aromatic, heteroaromatic, α,β-unsaturated, and aliphatic aldimines are all suitable. In general, aryl substituents, both electron rich and electron poor, give the best yields and enantiomeric excesses, although the presence of an ortho substituent on the ring does reduce yields and increase reaction times somewhat. Alkyl groups in general also give excellent results, again with an increase in reaction times for bulky substrates. However, unbranched aliphatic aldimines are not suitable substrates because they decompose under the reaction conditions. Heteroaromatic rings give good to excellent results, including even the rarely studied nitrogen-containing heterocycles pyridine and pyrrole.

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