49. Blanc Reaction-Blanc Rule

H. G. Blanc, Compt. Rend. 144, 1356 (1907).

Cyclization of dicarboxylic acids on heating with acetic anhydride to give either cyclic anhydrides or ketones depending on the respective positions of the carboxyl groups; 1,4- and 1,5-diacids yield anhydrides, while diacids in which the carboxy groups are in 1,6 or further removed positions yield ketones:

Chemical reaction

References

H. Kwart, K. King in The Chemistry of Carboxylic Acids and Esters, J. Patai, Ed. (Interscience, London, 1969) p 362; K. D. Bode, Houben-Weyl 7/2, 640 (1973). Cf. Ruzicka Large Ring Synthesis.