Ryan and Dunlea — Condensation of Aldehydes with 0-Diketones. 61 



In the presence of hydrochloric acid the latter compound changes into 

 the isomeride, 



CO 



which reacts with benzaldehyde and hydrochloric acid to form the unstable 

 red oxonium salt. 



H OCL 



CH CH 



CHC H 



« 5 



CHCHCl-C H 

 6 5 



This by loss of hydrochloric acid forms, first the chlorinated compound 



and then a . n'-diphenyl-/3-methyl-|3'-benzylidene-tetrahydro-'y-pyrone 



c H. CH 



The addition compound formed from this last with hydroxylamine must also be 



CHCH\ /CHCH'CH 



which belongs to a type of substances obtained by Harries [Ber. 30 (1897), 

 p. 230J from a-/3-unsaturated ketones. 



