Rhodium(III)-Catalyzed Redox-Neutral Synthesis of Isoquinolinium Salts via C–H Activation of Imines

Multicomponent Reactions Involving Diazo Reagents: A 5-Year Update

This review summarizes recent developments in multicomponent reactions of diazo compounds. The role of diazo reagent and the type of interaction between components was analyzed to structure the discussion. In contrast to previous reviews on related topics mostly focused on metal catalyzed transformations, a substantial amount of organocatalytic or catalyst-free methodologies is covered in this work.

Access to 5H-benzo[a]carbazol-6-ols and benzo[6,7]cyclohepta[1,2-b]indol-6-ols via rhodium-catalyzed C–H activation/carbenoid insertion/aldol-type cyclization

The rhodium-catalyzed mono-ortho C–H activation/carbenoid insertion/aldol-type cyclization of 3-aldehyde-2-phenyl-1H-indoles with diazo compounds has been developed.

First total synthesis of ampullosine, a unique isoquinoline alkaloid isolated from Sepedonium ampullosporum, and of the related permethylampullosine

A straightforward and convenient approach toward the first total synthesis of ampullosine, a structurally unique 3-methylisoquinoline alkaloid isolated from Sepedonium ampullosporum, is reported. Access to the related O-methyl ampullosine methyl ester from a common intermediate is also disclosed. The synthetic sequence toward the natural product comprised a Kolbe-type carboxylation of 3,5-dihydroxybenzoic acid and further esterification of the diacid, followed by masking of one of the phenols through selective ester reduction and subsequent acetonide formation. Installation of the three-carbon atom required for the 3-methylpyridine ring was performed by triflation of the remaining free phenol and a Pd-catalyzed Suzuki-Miyaura reaction with potassium E-propenyltrifluoroborate. Deprotection of the acetonide, followed by partial oxidation of the benzylic alcohol to the salicylaldehyde, O-methylation of the free phenol and hydrazonation of the resulting ortho-anisaldehyde derivative gave a hydrazone-based 1-azatriene. This was further subjected to 6π-azaelectrocyclization to afford permethylampullosine (11 steps, 14% overall yield), whereas exhaustive demethylation with AlI3 generated in situ gave ampullosine (12 steps, 3.2% global yield).

Rh(III)-Catalyzed C-C Coupling of Diverse Arenes and 4-Acyl-1-sulfonyltriazoles via C-H Activation

4-Acyl-1-sulfonyltriazoles act as versatile carbene reagents in Cp*Rh(III)-catalyzed ortho-selective coupling with arenes via C-H activation. The coupling led to olefination with possible cyclization, depending on the nature of the arene.

A Rh(iii)-catalyzed cascade C–H functionalization/cyclization reaction of salicylaldehydes with diazomalonates for the synthesis of 4-hydroxycoumarin derivatives

A cascade C–H functionalization/cyclization reaction of salicylaldehydes with α-diazomalonates has been developed for the synthesis of 4-hydroxycoumarin derivatives under rhodium(iii) catalysis.