A serendipitous
synthesis of N-substituted 2-amino-2′-hydroxy-1,1′-biaryls
through an aryne annulation with indolyl β-ketonitrile/ester
in a cascade manner is demonstrated. The reaction sequence involves
benzyne-mediated [2 + 2] Stoltz-type cycloaddition–cleavage
and intramolecular Michael addition followed by C–N bond cleavage
under transition-metal-free reaction conditions. Interestingly, while
[4 + 2] Diels–Alder reaction is a possible pathway, no traces
of the regioisomer was isolated.
Polyalkyl 2-cyanoacrylates begin to retropolymerize and deteriorate dramatically at temperatures above 80°C. They bond rapidly to the metal surfaces and readily lose strength even at ambient temperatures. These two drawbacks of the cyanoacrylates have made this class of adhesives unpopular as structural adhesives. Several attempts have been made to increase the thermal stability and the stability of the bond between the metal surfaces by adding chemicals like cyclopentadienoates and anhydrides to the cyanoacrylates. Cyclopentadienoates are not available commercially, and, therefore, in this study, we have selected various acrylates and methacrylates in the cyanoacrylate formulation and these were tested to various temperatures. Interesting results have been obtained and reported.
Rhodium catalyzed alkyne-tethered intramolecular annulation has been demonstrated for the synthesis of tetracyclic carbazole skeletons and successfully attained a series of five to eight-membered pyrido[3,2,1-jk]carbazoles. The present atom economic annulation...
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