Thiochromones thiochromanones

Treatment of dibromides 2 with sodium azide in N,N-dimethylformamide (DMF) at room temperature resulted in the formation of two products, 3-(a-azidobenzyOchromones 2a-c,g or -1-thiochromones 2d-f and the 3-arylidenechromanones la-c,g,h or -1-thiochromanones Id-f, respectively (eqn. 2). As shown by yield data given in Table 2, the substituent at position 2 plays decisive role in the product ratio. Dibromides unsubstituted at position 2 tended to give almost exclusively azides 3a-f and only a small amount of 1 was obtained. On the contrary, the reaction of flavanone derivatives 2gjh gave 3-arylideneflavanones... 

Oxidation of thiochromones does not lead to the sulfoxide or sulfone derivatives these are better prepared from the corresponding thiochromanones by oxidation followed by bromination and dehydrobromination. The 1-oxide is an extremely reactive species and gives a Diels-Alder adduct with butadiene. The 1,1-dioxide is also very reactive. Photolysis in benzene affords a 2 1 adduct in 30% yield (116) (79TL1097) via an initial [2 + 2] addition followed by a Diels-Alder reaction. Simple [2 + 2] addition is found with cyclohexene. 

Kumar et al. were successful to hydrogenate 2-substituted thiochromones (113) to thiochromanones (114) with use of an excess amount (30 wt%) of 10% Pd-C in ethyl acetate at room temperature, although the chromones with an electron-donating sub-... 

Thiochromone reacts with 2-piperidinobuta-1,3-diene to give a single diastereoisomeric thioxanthene-3,9-dione. Reaction of 4-silyloxy-l-benzothiopyrylium triflate, derived from thiochromone, with enamines involves regioselective 1,2-addition leading to 2-substituted thiochromanones <97JCS(P1)2807>. 

Thiochromanones, on photolysis (350 nm) in methanol, undergo not photoisomerization, such as is observed with 4-isothiochromanones, but photodehydrogenation to 4-thiochromones in moderate (50—55%) yield. 2-(t-Butylthio)-benzaldehyde (177), prepared in near quantitative yield from 0-nitrobenzaldehyde as indicated in Scheme 40, is a useful new synthon for thiocoumarins (178 R = CO2H, CONH2, C02Et, CN, Bz, Ph, or 2-thienyl) and benzo[l,2-f> 5,4-f> ]bisthiopyrans (179). ... 

Triphenylmethyl perchlorate added at 100° to a soln. of chromanone in glacial acetic acid-acetic anhydride (8 1) and the product isolated after ca. 30 min. - 4-hydroxybenzopyrylium perchlorate shaken with satd. NaHCOs-soln. chromone. Y almost 100%.—Similarly 6-Methyl-1-thiochromanone 6-methyl-1-thiochromone. Y 80%. F. e. s. A. Schonberg and G. Schiitz, B. 93, 1466 (1960) method s. Synth. Meth. 15, 698. 

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