Base-Catalyzed Efficient Tandem [3 + 3] and [3 + 2 + 1] Annulation-Aerobic Oxidative Benzannulations

Abstract

An efficient synthesis of substituted benzenes via a base-catalyzed [3 + 3] aerobic oxidative aromatization of α,β-unsaturated carbonyl compounds with dimethyl glutaconate was reported. All the reactions were carried out under mild, metal-free conditions to afford the products in high to excellent yields with molecular oxygen as the sole oxidant and water as the sole byproduct. Furthermore, a more convenient tandem [3 + 2 + 1] aerobic oxidative aromatization reaction was developed through the in situ generation of the α,β-unsaturated carbonyl compounds from aldehydes and ketones.

An Iron‐Catalyzed Cascade Approach to Benzo[b]carbazole Synthesis Followed by 1,4‐Sulfonyl Migration

“…Based on the literature [8,9,12,13] and our experimental results, we tentatively propose the reaction mechanism in Scheme 5. [14] Initially, the carbonyl group of 1 converted to its enol form A, and then the Lewis acid coordinated on the alkyne, which facilitates a 5-exo-dig cyclization and subsequent protodemetallation gives the vinylidene intermediate B.…”

“…[14] Initially, the carbonyl group of 1 converted to its enol form A, and then the Lewis acid coordinated on the alkyne, which facilitates a 5-exo-dig cyclization and subsequent protodemetallation gives the vinylidene intermediate B. Next, intermediate B converts to its enol form C and then undergoes a 6p electrocyclization, giving the intermediate D, and aerial oxidative aromatization [12] gave the hydroxy 5H-benzo [b] In summary, we have developed a simple and straightforward procedure for the synthesis of benzo [b]carbazoles by iron-catalyzed 5-exo-dig cyclization and a subsequent 6p electrocyclization. The reaction underwent an unprecedented [1,4]tosyl migration from nitrogen to oxygen with the aid of the same catalytic system.…”

Recent Progress in Transition‐Metal‐Free, Base‐Mediated Benzannulation Reactions for the Synthesis of a Diverse Range of Aromatic and Heteroaromatic Compounds

“…In 2012, the Zhao and Liu group performed efficient and atom‐economical benzannulation reactions for the construction of highly polysubstituted benzenes through base‐mediated [3+3] and [3+2+1] aerobic oxidative aromatization reactions (Scheme ) . The NaOH‐promoted benzannulation reaction of α,β‐unsaturated carbonyl derivatives 59 with dimethyl glutaconate 58 afforded polysubstituted benzenes 60 in good‐to‐excellent yields.…”

One‐Pot Synthesis of Phenanthridinones by Using a Base‐Catalyzed/Promoted Bicyclization of α,β‐Unsaturated Carbonyl Compounds with Dimethyl Glutaconate

“…The construction of distinct types of complex molecules from identical starting materials is an attractive and challenging task in organic synthesis 6. In our research on the syntheses of useful carbo‐ and heterocyclic compounds by employing readily available vinyl ketone precursors,7 we recently reported the one‐pot synthesis of polysubstituted benzenes 3 by using a based‐catalyzed [3+3] annulation reaction between α,β‐unsaturated carbonyl compounds 1 and dimethyl glutaconate ( 2 , Scheme , path A) 8. On the basis of these studies, we envisioned that compounds with a phenanthridinone core, such as dihydrophenanthridin‐6‐ones 4 and phenanthridin‐6‐ones 5b , could be constructed by a domino reaction involving an initial intermolecular [3+3] annulation reaction between α,β‐unsaturated carbonyl compounds 1 , which have a 2‐aminophenyl group at either the β‐position or carbonyl carbon, and dimethyl glutaconate 2 followed by an intramolecular aza‐cyclization/aromatization process under basic conditions (Scheme , path B).…”