(*) Part 11 : M. VANDEWALLE, S. DE WAELE and M. VERZELE; Bull. SOC. ... Chim. Belg., (in press). (**) This paper was ready to be sent to press when the synthesis by another route of 2-acetylcyclopentane-1,3-dione was described in a publication of F. ME ~ NYI and M. NILSON; Acra Chem. Scand., 17, 1801 (1963). (1) RJ LIGHT and Ch.R. HAUSER; J. Org. Chem., 26, 1296 (1961). (2) JH BOOTHE, RC WILKINSON, S. KUSHNER and JH ...