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The Fries rearrangement of dibenzofuran-2-yl ethanoate as a route to o-hydroxyacetyldibenzofurans has been investigated, both under thermal Lewis-acid catalysed and non-catalysed photochemical conditions. The reactions were examined theoretically at semi-empirical (PM3 and ZINDO/S) and density functional theory (DFT) levels. The correct selection of reaction conditions provides viable preparative routes to ortho-acylated hydroxydibenzofurans., Fundação para a Ciência e Tecnologia - PRAXIS/BD/19797/99. Fundação de Amparo à Pesquisa do Estado de Minas Gerais - Brasil. Conselho Nacional do Desenvolvimento Científico e Tecnológico (CNPq) - Brasil.

Several new spiro[thioxanthene-naphthopyrans] were prepared from substituted naphthols using a one step reaction. The photochromic properties of the new compounds were studied under flash photolysis and continuous irradiation. Compared to reference compounds general significant bathochromic shifts in the absorption spectra of the open forms, faster thermal bleaching kinetics and interesting fatigue resistances were observed.

The synthesis and photochromic properties, under flash photolysis and continuous irradiation, of new 2,2-diphenyl-2H-1-benzopyrans including a dibenzothiophene nucleus are described. Under flash photolysis, all compounds exhibit photochromic behaviour in solution at room temperature, but under continuous irradiation the same was not perceived. Compared to reference compounds, a general bathochromic shift and the existence of two absorption bands in the Vis spectra of the open forms, leading to a boardening in the absorption range, is observed. The heteroannellation effects on the spectrokinetic parameters are variable and depend on the position and geometry of the fused benzothiophene moiety. The effect of electron-withdrawing substituents in C(6) of the 2H-1-benzopyran skeleton, with the benzothiophene nucleus fused at the 7,8 positions, are analyzed.

The synthesis of 2 H -chromenes based on a fluorenone nucleus is described. Whereas 2,2-diphenyl-2 H -pyranofluorenones 4 – 7 and dicyanomethylidene-2 H -pyranofluorenes 8 – 10 do not exhibit photochromism, 2,2-diphenyl-2 H -pyranofluorenols exhibit photochromic behaviour. The spectrokinetic properties of these compounds in solution are reported.