607. Spirocyclic compounds. Part I. The preparation of compounds related to 3 : 2′-dioxogrisan

Abstract

By F. M. DEAN and KAMCHORN MANUNAPICHU.Alkylations of coumaran-3-ones generally lead to 2 : 2-disubstituted products some of which can be converted into spirocyclic compounds related to griseofulvin. Cyclisation was achieved only by acid-catalysed cyclodehydration; it led to 4 : 6 : 4'-trimethyl-(XXXII; Me for OMe) and 4 : 6-dimethoxy-4'-methyl-3 : 2'-dioxogris-3'-en (XXXII) . The latter compound was oriented by the production of 2-hydroxy-4 : 6-dimethoxybenzoic acid when the corresponding diol suffered periodate oxidation, which could include oxidation of hydrogen a t the %position of a coumaran-3-one. This type of oxidation has been realised in simple coumaranones and compared with the autoxidations of 2-alkyl-and 2-acetyl-coumaran-3-ones.ATTEMPTS to synthesise spirocyclic systems similar to those of griseofulvin (I) and the derivative (11) of usnolic acid 2 from coumaranones of type (IV) have led to spirocyclic diketones of type (111).Addition of vinyl cyanide to 4 : 6-dimethoxycoumaran-3-one (IV; R = OMe) led only to the dicyanide (V; R = OMe), which had the appropriate absorption bands a t 2257 (EN) and 1698 crn.-l (coumaranone CO), and the same ultraviolet absorption as the parent dimethoxycoumaranone. In contrast, no reaction with ally1 cyanide could be realised in spite of reports by Michael and Ross 3 and Bruson.4 Similarly, the dicyanide (V; R = Me) was easily prepared from 4 : 6-dimethylcoumaran-3-one (IV; R = Me) and appeared to be suitable for cyclisation to a derivative of cyclohexanone by the technique of Ziegler, Eberle, and Ohlinger. This dicyanide, however, resisted cyclisation by lithium ethylanilide, and was therefore hydrolysed to the dibasic acid (VI; R = Me, R' = H) ; the acid, however, was not cyclised by acetic anhydride, nor did its ester (VI; R = R' = Me) undergo the Dieckmann reaction. Attention was therefore directed to 2-acylcoumaran-3-ones in which but one incoming substituent could be accommodated at the 2-position.The glyoxylic ester (VII) formed from the coumaranone (IV; R = Me) and ethyl Grove, MacMillan, Mulholland, and Rogers, I., 1952, 3977.