Thiochromans and Related Compounds

Catalytic reduction of 2,2-dimethylthiochroman-4 one in the presence of sulphuric acid gives the corresponding thiochroman in high yield, but in the absence of the acid a mixture of products is formed. The reduction of thiochroman-4-one oximes to 4-aminothiochromans has also been reported.  

The detailed structure of the clathrate compound formed between 2,5,5-trimethylhex-3-yn-2-ol and 4-p hydroxyphenyl-2,2,4-trimethylthio chroman has been determined by A -ray crystallography. tra/i5 -3,4-Dibromothiochroman and analogous dibromo-naphthothio-pyrans, prepared by addition of bromine to the appropriate A -thio-chromenes, may exist in sofa conformations. The dibromo-compounds undergo ring-contraction reactions with alkalis, yielding benzo[ ]thiophen derivatives.  

A -Thiochromenes (53 R = H or Me) have been prepared by the action of heat on the acetylenes (52 R = H or Me), and the cyclization of nitriles of type (54 X = CN or C02Et) with aluminium bromide leads to A -thiochromene derivatives (55).  

Various reactions have been reported for thiochroman-4-ones the Schmidt reaction brings about ring expansion to lactams of the 1,4- and 1,5-benzothiazepine series the stereochemistry of bromination of 6-methyl-2-phenylthiochroman-4-one and its 1,1-dioxide has been investigated treatment of thiochroman-4-ones with dimethyloxosulphonium 

Cyclization of the thiochroman (60) with sulphuric acid yields a mixture of the tricyclic ketone (61) and its dihydro- and dehydro-derivatives. Irradiation of the sulphoxide (62) gives the products shown mono-3-substituted analogues of (62) behave similarly, but 2-phenyl- and 2,2-dimethylthiochroman-4-one sulphoxides are converted into ring-contracted products and much polymeric material.  

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