anti-Aminoallylation of Aldehydes via Ruthenium-Catalyzed Transfer Hydrogenative Coupling of Sulfonamido Allenes: 1,2-Aminoalcohols

Abstract

Ruthenium-catalyzed transfer hydrogenation of N-sulfonamido allene 1e in the presence of aromatic aldehydes 2a−f, α,β-unsaturated aldehydes 2g−i, and aliphatic aldehydes 2j−l results in reductive coupling to furnish the corresponding anti-aminoallylation products 3a−l. Reductive coupling of allenamide 1e to aldehyde 2a conducted using 2-propanol-d₈ as the terminal reductant delivers deuterio-3a. The observed pattern of deuterium incorporation suggests reversible allene hydrometalation with incomplete regioselectivity in advance of carbonyl addition. A survey of monosubstituted allenes 1f−i was conducted. High levels of anti-diastereoselectivity were observed only when tert-butyl allene 1f was used. This protocol represents an alternative to the use of amino-substituted allylborane reagents in carbonyl aminoallylation and avoids the use of stoichiometric metallic reagents.