Chromans thiochroman-4-ones

The infrared spectra and dielectric constants,101,102 electronic,103-111 nuclear magnetic resonance (NMR),106,112-121 and mass122-126 spectral data for these compounds have been analyzed. There exist numerous quantum mechanical calculations of the electronic transitions and involvement of the sulfur electrons.107,111 Ultraviolet spectral determinations of the basicity of thiochroman-4-ones110 allowed correlations with the corresponding chroman-4-ones. 

The intramolecular Friedel-Crafts cyclization of 3-(4-chlorophenylthio)butanoic acid to 6-chloro-2-methylthio-chroman-4-one is efficiently catalyzed by Bi and rare-earth triflates (Equation 195) <2003TL4007>. The cyclization of (3-arylthiopropanoic acids to thiochroman-4-ones by PPA is facilitated by microwave irradiation. Formation of these acids from the sodium salts of thiophenols and 3-chloropropanoic acid is similarly accelerated <2004JCM394>. 

The alkylidene malononitrile derived from chroman-4-one adds to /ra .v-P-nitrostyrcne to give (5, /< )-2-[3-(2-nitro-l-phcnylcthyl)chroman-4-ylidene]malononitrile under dihydroquinine catalysis (Scheme 39) <06OBC63> and a similar reaction of both the chromanone and thiochroman-4-one dicyanoalkenes with a,P-unsaturated aldehydes proceeds with even better ee <06CC1563>. 

Many 3-dialkylaminomethyl- and 5-dialkylaminoalkylaminothio-chroman-4-ones exhibit schistosomicidal activity,and a variety of other aminothiochromans are antiamebic. " The thiochroman ring is also found in antimicrobial agents,virucides, insecticides, and acaricides, and antiedemic and anti-inflammatory agents. Hexahydrothiochroman has been employed as a fuel additive, and several <-butyl thiochroman-4-ones have been studied for their... 

The dehydrogenation of 2 -hydroxychalcones and flavanones to flavones, of l-(2-hydroxyaryl)alk-2-en-l-ones and chroman-4-ones to chromones and of thiochroman-4-ones to thiochromones can be accomplished using iodine in hot DMSO <97HCM223>. E-3-Styrylchromones result from the oxidative rearrangement of 5-aryl-l-(2-hydroxyphenyl)penta-2,4-dien-l-ones with thallium(lll) nitrate <97LA2065>. Dimethyldioxirane converts flavanones into flavones by way of the 2-hydroxyflavanone. This approach enables flavans to be converted to a variety of flavonoids <97TL4651>. 

Thiochromans and Thiochromones.—The spirothiochroman (175) has been synthesized from 3-methylene-l/7-2-benzothiopyran-4(3//)-one (176) and its stereochemistry has been examined, using X-ray crystallography. Modifications which have been made to Dianin s compound (see also under Chromans ) include replacement of the ring oxygen by sulphur. Some such compounds retain the clathrate-forming ability of the original molecule. 

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