Rhodium-Catalyzed Enal Transfer with N-Methoxypyridazinium Salts

Abstract

Herein, we report a simple method for functionalized enals involving enal-transfer reaction of water-soluble N-methoxypyridazinium salts. This open-flask reaction proceeds under mild aqueous basic conditions through [2,3]-sigmatropic rearrangement of propargyl/allyl sulfur-ylides derived from in situ-generated Rh-(E)-enalcarbene. Various synthetically challenging allene- and allyl-functionalized (E)-enals with a γ-C­(sp3) quaternary center were obtained in good to high yields. InCl3-catalyzed cascade cyclization of allenyl-enal and aniline gave a valuable pyrrolo­[1,2-a]­quinoline motif.

Triple Nucleophilic Head-to-Tail Cascade Polycyclization of Diazodienals via Combination Catalysis: Direct Access to Cyclopentane Fused Aza-Polycycles with Six-Contiguous Stereocenters

“…Initial investigations by us and others revealed that (2 E )-diazoenals (n = 1) are versatile substrates for metal catalysis and combinations catalysis. − Rh-enalcarbenoid reacts with a variety of π- and heteroatom nucleophiles resulting in the (4 + 2), ,,, (4 + 1), (1 + 1 + 3), (3 + 3), and (3 + 2) annulations, olefination, and enal-transfer reactions. Notably, the reaction of diazoenal and N -aryl propargylamine under combination catalysis gave enal-functionalized 1,4-oxazines via cascade Rh-carbenoid NH-insertion and remote 6- exo-dig heterocyclization enabled by synergistic Au­(I) and dienamine catalysis (Figure D) …”

Catalytic [2,3]-sigmatropic rearrangement of sulfonium ylides derived from azoalkenes: non-carbenoid Doyle–Kirmse reaction

“…6 Significant progress has been made in the past few decades. 7 However, the conventional Doyle–Kirmse reaction makes use of diazo compounds which are usually hazardous and explosive, and requires stringent reaction conditions due to the high reactivity of the metal carbenoid intermediates. So, its synthetic utility has been somewhat limited.…”