Studies of the Reaction of Various 1,2-Disubstituted Benzenes with Crotonic Acid in Polyphosphoric Acid

H a m i s h G . G r a n t * Department o f Organic Chemistry, University o f Adelaide G . P . O . B o x 498, South Australia 5001 Z. Naturforsch. 34b , 728-733 (1979); received N o v e m b e r 27, 1978 5,6-Disubstituted Indanl -ones , Crotonic Ac id , Po lyphosphor i c Ac id , 1-Methyl Benzofurocyc lopentan-3-one, 1 3C N M R The reaction of several 1,2-disubstituted benzenes with crotonic acid in po lyphosphor ic acid has provided a number of previously undescribed 5,6-disubstituted indanl -ones . Guaiacol , o-cresol, 1,3-benzodioxole, 1,4-benzodioxan and d ihydrobenzofuran yielded indanones (4 -8) in which acylation of the benzene ring occurred exclusively para to the free hydroxy l groups of the first two substrates and para t o the ether o x y g e n in the last. Catechol , salicylaldehyde, o h y d r o x y acetophenone and o-chloro phenol yielded no indanones and formed crotonate esters. A further four indanones (9 -12) were derived f rom demethylat ion and acetylation procedures. Annelation of the methyl cyc lopentanone ring occurred acrose the furan ring in benzofuran to provide the new heterocycle 1-methyl benzofurocyc lopentan-3-one in moderate yield. The assigned carbon1 3 N M R spectral shifts for all indanones are set out in Table I I .