Synthesis of Stable N–H Imines with a Benzo[7,8]indolizine Core and Benzo[7,8]indolizino[1,2-c]quinolines via Copper-Catalyzed Annulation of α,β-Unsaturated O-Acyl Ketoximes with Isoquinolinium N-Ylides

Abstract

A copper-catalyzed annulation of α,β-unsaturated O-acyl ketoximes with isoquinolinium N-ylides has been developed for the concise synthesis of stable N–H imines with a benzo­[7,8]­indolizine core. When β-(2-bromoaryl)-α,β-unsaturated O-acyl ketoximes are used as the starting materials, a cascade cyclization occurs to afford the benzo­[7,8]­indolizino­[1,2-c]­quinolines.

Divergent synthesis of two types of indolizines from pyridine-2-acetonitrile, (hetero)arylglyoxal, and TMSCN

“…Due to the growing interest in indolizine-embedded polycycles, many synthetic methods have been disclosed including [3 + 2] annulation approaches with pyridinium ylides and alkenes/alkynes. 4 Recently, we have communicated on the construction of two indolizines fused with pyrrolo[1,2- a ]pyrimidine and indole ( 2 and 4 ), respectively, both of which employed one-pot three-component coupling to obtain 3-amino-1-cyanoindolizines ( 1 and 3 ) as intermediates (Scheme 1a). 5,6 The subsequent oxidative cyclization of 1 and Ullmann-type double C–N coupling of 3 furnished 2 and 4 , respectively.…”

Photoinduced sulfonylation cyclization to medium-sized benzo[b]azocine and mechanistic insight

“…8 Reported studies of these photochemical-driven radical cyclization reactions have focused on building energetically favorable five- or six-membered heterocyclic products. 9,10 However, largely because of inherent unfavorable enthalpy and entropy factors, reports of medium-sized N-heterocycle construction via radical reactions are rare, 11 and the synthesis of eight-membered benzo[ b ]azocines using photochemical methods has not yet been substantiated.…”

“…Because of our particular interest in nitrogen heterocyclic chemistry, 13 in this study we designed a series of dienes and investigated their use in the synthesis of important eight-membered benzo[ b ]azocine derivatives via a novel photochemically driven, sulfonyl-centered, radical-initiated tandem cyclization that involves a chemoregioselective 8-endo cyclization-addition. Energetically favorable sulfonyl-radical cascade cyclizations to five- or six-membered N-heterocycles (Scheme 1a) 9,10 and azocines synthesis via ionic reactions have been reported. 2–5 However, this is the first example of the synthesis of structurally diverse sulfonylbenzo[ b ]azepines via a sulfonyl-radical-initiated ordered 8-endo cyclization-addition reaction (Scheme 1b).…”

Concise synthesis of pyrrolo[3,4-c]quinolines via a P(NMe2)3-catalyzed [4 + 2] annulation followed by a Zn/AcOH-mediated reduction–hydroamination–isomerization

“…1 e In addition, compounds VII and VIII have been described as potent inhibitors of caspase-3, 1 f in particular, VIII plays a key role in apoptosis. 2 Based on the importance of the aforementioned valuable biological and pharmacological activities, a series of synthetic approaches, including traditional methods, 3 metal catalysis, 4 and photocatalysis, 5 have been developed for the creation of pyrrolo[3,4- c ]quinolines. However, to the best of our knowledge, the organocatalytic strategy is rarely reported and still highly challenging.…”