Spiro -5-methylbenzo

Reactions of the Side-chain of Benzothiophens.—The C n.m.r. chemical shifts in 2-benzo[ j]thenyl carbenium ions have been investigated.The thermal decomposition of 2-azidophenyl 2-(3-methylbenzo[ >]thienyl) sulphide and of 2-azidophenyl 3-(2-methylbenzo[ ]thienyl) sulphide proceeded efficiently through spiro-benzothiazolines to give (161) and (162). 5-Hydroxy-3-methyl-benzo[ ]thiophen-2-carboxylic acid is most conveniently decarboxylated by refluxing with 48% hydrobromic acid. The decomposition of benzo[/)]thiophen-2(3//)-one and of 3-diazobenzo[/ ]thiophen-2-one at high temperatures provided convenient syntheses of benzothiet and the transient benzothiet keten. The decomposition reactions were carried out in the reactor of a photoelectron spectrometer.Heterotriptycenes have been obtained from... 

Dihydro-5,8-dihydroxy-6,6 -dimethoxy-4 -methylnaphthaIene-2-spiro-2 -2 /7-benzofuran-l,3, 4-trione in nitrobenzene heated at 200° for 2 h->- 6,ll-dihydroxy-3,8-dimethoxy-l-methylbenzo[Z ]xanthene-7,10,12-trione. Y 74%. F.e.s. C.B. de Koning et al., J. Chem. Soc. Perkin Trans. I 1988, 3209-16. 

In addition, a versatile route to benzodiazocine and spiropyran derivatives via chalcones was reported (13JCS517). The synthesis of spiro[o-thiophene-5, 6 -diphenyl-2H-pyran-4, 3 ] -5-methylbenzo [b] thio-phene-2-one from thioisatins is shown below. The broad scope of usable substrates of industrial relevance is discussed. 

Preparation by reduction of 2, 4, 6,6 -tetramethoxy-5-methyl-spiro [81574-66-51-3(2, 4 -dione (SM) with zinc dust in acetic acid for 1 h (85%). SM was prepared from methyl 2,4-dimethoxy-6-(2,4,6-trimethoxy-phenoxy)-3-methylbenzoate by treatment with titanium tetrachloride and hydrogen chloride for 65 h (78%, m.p. 265-267°) [1184],... 

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