Synthesis of allenes via CuBr-catalyzed homologation of alk-1-ynes accelerated by microwave

CuI‐Catalyzed Synthesis of Functionalized Terminal Allenes from 1‐Alkynes

“…and CuI (0.5 equiv. ), and the work of Nakamura,5d which decreased the amount of CuBr catalyst to 0.3 equiv., but required high temperatures and microwave irradiation, this protocol has the obvious advantage with respect of the amount of catalyst and paraformaldehyde. It should be noted that all reactions in this study were carried out without the protection of an inert atmosphere.…”

Can the Crabbé Homologation Be Successfully Applied to the Synthesis of 1,3-Disubstituted Allenes?

“…The results of the reaction using other amines than dicyclohexylamine were in good agreement with the previously reported tendency in the original Crabbé reaction. 1,3,4 Thus, the use of diisopropylamine resulted in a lower yield of the allene, and both reactions using morpholine and dibenzylamine afforded only a trace amount of the desired product (Scheme 2).…”

“…Recently, the improved Crabbé homologation was independently reported by two groups. Nakamura and co-workers found that the microwave (MW) irradiation accelerated the reaction, 3 whereas Ma and co-workers found that replacing 3a and copper(I) bromide with N,N-dicyclohexylamine (3b, R 2 = Cy) and copper(I) iodide, respectively, led to an increase in the chemical yields of the allenes. 4…”

Theoretical Studies of Allene Synthesis through Cadmium Iodide‐Mediated Allenylation of Terminal Alkynes

“…In the past, there has been much effort to develop synthetic methods for their preparation . Among these approaches, the metal‐promoted allenylation of terminal alkynes (ATA) with aldehydes in the presence of amines has emerged as a practical synthetic method for the construction of substituted allenes . By using ATA reactions, mono‐,, 1,3‐di‐, and trisubstituted allenes are now easily prepared from terminal alkynes, aldehydes or ketones, and amines.…”