MW-Assisted Passerini Reaction

The results obtained in this study in terms of reaction time (Imin or less at 120°C) are remarkable as compared with our previous results on the Passerini reaction using, for instance, ionic liquids (2-14h) [61], PEG (0.5-6h) [61], CH Cl (18h) [57a], or water (3-3.5 h) [57a]. All these alternative solvents have been found to be efficient in this reaction, but in all cases, longer reaction times were required and lower yields were achieved. 

SCHEME 8.27 Isatin derivatives synthesized following a Passerini 3CR. 

1 (a) M. Passerini, Gazi. Chim. Ital. 1921, 51, 126-129. Sopra gli isonitrili (1). Composto delp-isonitrili-azobenzole con acetone ed acido acetica. (b) M. Passerini, Gozz. Chim. Ital. 1921, 51, 181-188. Sopra gU isonitrili (11). Composti con aldeidi o con chetoni ed acidi organic monobasic . 

2 (a) L. Banfi, R. Riva in Organic reactions (A. B. Charette, Ed.). John Wiley Sons, Inc., Hoboken, NJ, 2005, Vol. 65, pp. 1-140. The Passerini reaction, (b) L. Banfi, R. Riva, A. Basso, Synlett 2010, 23-41. Coupling isocyanide-based multicomponent reactions with aliphatic or acyl nucleophilic substitution processes, (c) S. Sadjadi, M. M. Heravi, Tetrahedron 2011, 67, 2707-2752. Recent application of isocyanides in synthesis of heterocycles. 

Kazemizadeh, A. Ramazani, Cum Org. Chem. 2012,16, 418 50. Synthetic applications of Passerini reaction. 

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Contemporaneously, the use of microwave as promoter chemical reactions has become increasingly popular in organic synthesis [68]. This tool has been demonstrated to be efficient for increasing the rate of MCR reactions reducing the reaction times and improving the yields [69, 70], However, the first example of MW-assisted Passerini reaction has been only recently disclosed (Scheme 8.28) [71]. 

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