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Synthesis of chromones, annulated with oxygen-containing heterocycles with two hetero atoms at C(7)-C(8) bond

“…The first one was realized in the synthesis of bausplendin 2a and its analogues 2b,c, which were synthesized from the corresponding 7,8-dihydroxyflavones by alkylation with diiodomethane [5], dibromomethane [10] or methylene sulfate [5], K2CO3 [11] or KF [10] (Scheme 1). [12,13] and dibromomethane [8,14,15] in the presence of K2CO3. When heated in acetone or dioxane, the reaction was completed in 36 [12] and 15 hours [8], respectively.…”

“…When heated in acetone or dioxane, the reaction was completed in 36 [12] and 15 hours [8], respectively. When DMF [8,14,15] or its mixture with acetone [13] has been used as a solvent, the reaction time was reduced to 1,5-2 h and yield of target products was increased (Scheme 2). which on oxidation with I2 in DMSO gave 7,8-methylenedioxyflavones 13 [9,17,18] (Scheme 5).…”

“…The synthesis of 2,3-dihydro-7H- [1,4]dioxino [2,3-h]chromen-7-ones starting from 3-hydroxymethyl-5-hydroxy-6-acetylbenzodioxane 1.3. 3,4]dioxepino [2,3- 3,4-dihydro-2H,8H- [1,4]dioxepino [2,3-h]chromen-8-ones 36 were formed [8,14,15] (Scheme 14). Scheme 18.…”

Arylation of ortho-Hydroxyarylenaminones by Sulfonium Salts and Arenesulfonyl Chlorides: An Access to Isoflavones

“…At the same time, other strategies like (iv) [3 + 3]-cyclizations, (v) [5 + 1]-cyclizations, and (vi) intermolecular cyclizations of appropriate linear precursors constitute a vast set of reaction used for preparation of the title heterocycles. On the other hand, more obsolete strategies which have no practical applications nowadays were also utilized. , Many of the presented tactics are tedious multistep routes which involve cumbersome procedures, in some cases with poor functional group tolerance and insufficient efficiency. Thus, there is a growing need of new synthetic tactics which can address the current challenges in concise preparation of 3-arylchromones.…”