Ring transformations of heterocyclic compounds. XVI. Spiro[cyclohexadiene-dihydroacridines]. A novel class of spirodihydroacridines by ring transformation of pyrylium salts with 9-methylacridine and its quaternary salts

摘要

2,4,6-Triarylpyrylium salts 1 react with the in situ generated anhydrobase of 9, 10-dimethylacridinium methosulfate (2a) in the presence of anhydrous sodium acetate in ethanol by a 2,5-[C-4+C-2] pyrylium ring transformation to give the hitherto unknown 6-aroyl-3,5-diaryl-10'-methylspiro[cyclohexa-2,4-diene-1,9'-9',10'-dihydro acridines] 3. When the pyrylium perchlorate la is treated under the same conditions with the N-ethyl, N-allyl or N-benzyl substituted acridinium salts 2b-d a dealkylation ol these salts occurs and the N-unsubstituted spiro[cyclohexadiene-dihydroacridine] 4a is formed. The same compounds 4 can also be obtained by transformation of the pyrylium salts 1 with 9-methylacridine (7) and triethylamine/acetic acid in ethanol. Structure elucidation is performed by an X-ray crystal structure determination of the spiro[cyclohexadiene-dihydroacridine] 3a. Spectroscopic data of the transformation products and their mode of formation are discussed. [References: 43]