Selective Functionalization of Aromatic C(sp<sup>2</sup>)−H Bonds in the Presence of Benzylic C(sp<sup>3</sup>)−H Bonds by Electron‐Deficient Carbenoids Generated from 4‐Acyl‐1‐Sulfonyl‐1,2,3‐Triazoles

A chemoselective tandem reaction of 4acyloxymethylene-1-sulfonyl-1,2,3-triazole and vinyl ether was reported, producing polysubstituted piperidine derivatives in up to 96% yield. The key intermediate N-sulfonyl 1-azadiene generated by migration of the OAc group to the a-imino rhodium carbene was isolated and a plausible mechanism was proposed. Several related ring systems were constructed from the highly functionalized products.

Synthesis of Piperidine Derivatives by Rhodium‐ Catalyzed Tandem Reaction of N‐Sulfonyl‐1,2,3‐Triazole and Vinyl Ether

Wang

et al. 2018

TBAI or KI‐Promoted Oxidative Coupling of Enamines and N‐Tosylhydrazine: An Unconventional Method toward 1,5‐ and 1,4,5‐Substituted 1,2,3‐Triazoles

Huang

Zhu

et al. 2018

A novel method for the synthesis of 1,5‐ and 1,4,5‐substituted 1,2,3‐triazoles has been reported. This approach is promoted by iodine‐TBHP oxidation system using enamines and N‐tosylhydrazine as materials, which avoid the dependence of traditional methods on azides and transition metals. Through this approach, various 1,5‐ and 1,4,5‐substituted 1,2,3‐triazoles were delivered in moderate to high yields. The mechanistic study indicated that an amino exchange would be involved in the reaction process. Moreover, the product methyl 1‐(2‐methoxyphenyl)‐4‐methyl‐1H‐1,2,3‐triazole‐5‐carboxylate is a useful precursor to anti‐influenza A agent, and further application research was conducted.magnified image

Synthesis of α‐(2‐Hydroxyphenyl)‐α‐Aminoketones by Rhodium‐Catalyzed Tandem Reaction of 1‐Sulfonyl‐1,2,3‐Triazoles and Benzoquinone‐Derived Alcohols

Wang

Cen

et al. 2020

Readily available 1‐sulfonyl‐1,2,3‐triazole and benzoquinone‐derived alcohols were employed in a synthesis protocol for the formation of α‐(2‐hydroxyphenyl)‐α‐aminoketone. The cascade reaction includes the formation of rhodium carbene, O−H bond 1,3‐insertion, Claisen rearrangement as well as aromatization. Valuable benzoxazinone and 3‐aminobenzofuran were obtained after one‐step derivatization. Moreover, an estrone derivative was modified via the protocol with extraordinary efficiency.magnified image