Gold‐catalyzed [4+3]‐Annulations of Benzopyriliums with Vinyldiazo Carbonyls to Form Bicyclic Heptatriene Rings with Skeletal Rearrangement

Abstract

We report gold catalyzed [4+3]‐annulations between benzopyriliums and 3‐alkyl‐2‐diazo‐3‐vinyl carbonyls, yielding 7H‐benzo[7]annulene products efficiently. Notably, the carbon skeletons of resulting 7H‐benzo[7]annulenes are structurally rearranged, accompanied by migrations of their alkyl and ketone motifs. Apart from applicable substrates over a wide scope, these annulatios are applicable to pyriliums and 3‐alkyl‐2‐diazo‐3‐vinyl esters to increase their reaction significance. We postulate a mechanism involving an initial [4+2]‐cycloaddition between benzopyriliums and 3‐alkyl‐2‐diazo‐3‐vinyl carbonyl species, followed by formation of gold carbenes to induce a ring expansion and group migrations.

Mechanistic duality of indolyl 1,3-heteroatom transposition

“…3A ). 15 The involvement of the concerted pathway should result in the exclusive migration of 18 O to the 3-position of pyrroloindoline ( 18 O-2a), the involvement of the dissociative pathway should produce a mixture of products: 18 O-2a and 18 O-2b, in which the 18 O labelling is evenly distributed between the C3-oxygen and the carbonyl oxygen. Based on these assumptions, a series of 18 O-enriched indolyl benzoates with different electron-withdrawing capacities were prepared ( Fig.…”

Recent Advances in Gold-Catalyzed Transformations of Vinyldiazo Reagents

“…Thus, gold-catalyzed reactions of 2-alkynylbenzaldehydes and 3-alkyl-2-diazo-3-vinylketones furnished bicyclic heptatriene derivatives. 41 In a further example of the participation of vinyldiazo ketones as nucleophilic partners, Liu and co-workers reported the gold-catalyzed reaction of N-(2-ethynylphenyl)aldimines with vinyldiazo ketones to yield unsymmetrical triarylmethane derivatives featuring indole and furan moieties (Scheme 26). 42 The key steps in the proposed mechanism are: (1) initial cyclization of the aldimine reagent with formation of an azomethine ylide intermediate; The formation of two heterocyclic systems in a single and operationally simple synthetic operation has been also achieved by Liu's group via the gold-catalyzed reaction of 2-(1-alkynyl)-2-alken-1-ones and vinyldiazo ketones (Scheme 27).…”

“…Thus, gold-catalyzed reactions of 2-alkynylbenzaldehydes and 3-alkyl-2-diazo-3-vinylketones furnished bicyclic heptatriene derivatives. 41…”