Improved Buchner reaction selectivity in the copper-catalyzed reactions of ethyl 3-arylmethylamino-2-diazo-3-oxopropanoates

Iron: A Worthy Contender in Metal Carbene Chemistry

“…Somewhat limited reactivity was also found for C–H and O–H insertions and some multicomponent reactions (Figure – orange). Still, there is work remaining; looking at the “neighbor’s lawn”, we see copper-catalyzed borylation, Buchner reactions, or halogenations . We see dirhodium catalysts used in multicomponent reactions to afford high complex products .…”

“…The complexation of a Cr(CO) 3 group to the aryl aldehyde was a key factor in inducing selectivity. This compound was then treated with trimethylsilyl triflate, generating a chiral iron carbene intermediate (153) that promptly reacted with an alkene in solution to form the desired cyclopropane (154) in cis/trans-ratios above 6:1 and exceptional enantioselectivity (ee > 95%). Exposure to natural sunlight was then sufficient to dissociate the chromium complex and obtain the final product (155), a precursor to the antibiotic cilastatin.…”

Skeletal Editing of (Hetero)Arenes Using Carbenes

“…According to the DFT calculations, the reaction initiated the dehydration of o ‐hydroxyl‐benzyl alcohol via a Brønsted acid‐mediated proton shuttle transition state to form an o ‐quinone methide intermediate (Scheme 25b) [119] . Xu and coworkers also found that the presence of N ‐substituent on the ethyl 3‐arylmethylamino‐2‐diazo‐3‐oxopropanoates could improve the Buchner reaction selectivity [120] . Recently, the Che group described the intramolecular Buchner reaction and cyclopropanation of alkyl diazomethanes generated from N ‐tosylhydrazones catalyzed by cobalt(II)‐porphyrin.…”

“…[119] Xu and coworkers also found that the presence of N-substituent on the ethyl 3-arylmethylamino-2-diazo-3-oxopropanoates could improve the Buchner reaction selectivity. [120] Recently, the Che group described the intramolecular Buchner reaction and cyclopropanation of alkyl diazomethanes generated from N-tosylhydrazones catalyzed by cobalt(II)-porphyrin. A range of bicyclic cycloheptatriene fused pyrrolidines and tetracyclic cyclopropane fused pyrrolidines were obtained in good to high yields with high chemo-and regioselectivities (Scheme 25c).…”

Rhodium-Catalyzed 1,1-Hydroacylation of Thioacyl Carbenes with Alkynyl Aldehydes and Subsequent Cyclization

“…Previous hydroacylation reactions occurred across an unsaturated CX (X = C or O) double or CC triple bond (1,2-hydroacylation). Out of our cabene chemistry background, , we found that reports on hydroacylation at an unsaturated carbene center (1,1-hydroacylation) are quite rare, although it provides a novel access to carbon homologation (Scheme a, v). It must be noted that in 2016 Yao and Lin reported the annulation between salicylaldehydes and acyl carbenes, and a 1,1-hydroacylation was proposed in the mechanism (Scheme b) .…”