Direct aromatic tert-butylation during the synthesis of thiochroman-4-ones

Stereoselective Synthesis of Thiochroman-4-ones by Ring Transformation of Chiral 5-Ylidene-1,3-dioxan-4-ones with 2-Bromothiophenol via Bromo−Lithium Exchange

“…Data for the racemic 5a [5,6,9] and (2R)-5a [1] have been reported earlier. [9] Ϫ Yield: 144 mg (75%).…”

“…The most versatile route to thiochroman-4-ones is based on the addition of arylthiols to α,β-unsaturated carboxylic acids or their derivatives, followed by intramolecular Friedel-Craft acylation of the resulting β-arylthiopropionic acids. [3,5,6] The latter can also be obtained in other ways such as by the ring opening of β-lactones. [5] The only reported synthesis of optically active thiochroman-4-ones uses the cyclization of (R)-β-phenylthiocarboxylic acids which were obtained from optically active β-hydroxy esters and thiophenol.…”

“…[3,5,6] The latter can also be obtained in other ways such as by the ring opening of β-lactones. [5] The only reported synthesis of optically active thiochroman-4-ones uses the cyclization of (R)-β-phenylthiocarboxylic acids which were obtained from optically active β-hydroxy esters and thiophenol. [1] Racemic 2-phenyl-thiochroman-4-one has been resolved by formation of its chiral hydrazone.…”

A Novel Synthesis of Heterocyclic Analogues of Thioflavanones from Haloheteroaromatic Carboxylic Acids

“…8 Another thioflavanone synthesis involved intramolecular cyclization of 2'-mercaptochalcones, which are prepared by the base catalyzed condensation of 2'-benzylthioacetophenones and benzaldehydes followed by subsequent debenzylation, with p-toluenesulfonic acid 9 or phosphomolybdic acid supported on silica (PMA-SiO 2 ). 10 The cyclization of S-benzyl protected α-sulfinyl chalcones followed by debenzylation with formic acid proceeds smoothly to give 3-sulfinylthioflavanones.…”

A New Synthesis of Thioflavanones from Thiosalicylic Acid

“…5 The construction of thiochroman-4-one rings is also performed by the acyl radical cyclization of 2-allylthiotriphenylhydrazides 6 at high temperature in multiple steps from thiosalicylic acid. Alternatively, thioflavanones are synthesized by the catalytic hydrogenation 7 of thioflavones, derived from the condensation of thiophenols and β-keto esters 8 or the intramolecular Wittig cyclization of salicilate thioesters, 9 with H 2 /Pd-C, but the desired products are obtained in low yields with side products.…”