Potassium Hydroxide → HCID 22404755, compound

Participants

Reaction Steps

Schema 6 illustrates the synthesis of an amino substituted 2,2-dialkyl-2H-1-benzopyran and an amino substituted 2,2-dialkyl-3,4-dihydro-2H-1-benzopyran, for example, 8-amino-5-chloro-7-fluoro-2H-1-benzopyran and 8-amino-5-chloro-3,4-dihydro-7-fluoro-2H-1-benzopyran by the reaction of an appropriately substituted 2-fluorobenzonitrile with 2-methyl-3-butyn-2-ol under basic conditions in dimethyl sulfoxide, yielding the corresponding 3-(2-cyano-substituted-phenoxy)-3-methyl-1-butyne (XXI). The butyne intermediate is then cyclized at 180° C. in 1,2-dichlorobenzene, giving the appropriate 8-cyano-2,2-dialkyl-7-fluoro-2H-1-benzopyran, for example, 8-cyano-2,2-dimethyl-7-fluoro-2H-1-benzopyran (XXII), which is in turn treated with potassium hydroxide in t-butanol, yielding 2,2-dimethyl-7-fluoro-2H-1-benzopyran-8-ylcarboxamide (XXIII). The so-prepared carboxamide is then reduced with sodium hypochlorite and sodium hydroxide in water and dioxane, affording the corresponding free amine, for example, 8-amino-2,2-dimethyl-7-fluoro-2H-1-benzopyran (XXIV). The intermediate benzopyran is optionally halogenated in the 5-position as described above, yielding the corresponding benzopyran intermediate, for example, 8-amino-5-chloro-2,2-dimethyl-7-fluoro-2H-1-benzopyran (XXV). To obtain an amino substituted 2,2-dialkyl-3,4-dihydro-2H-1-benzopyran, for example, 8-amino-5-chloro-3,4-dihydro-7-fluoro-2H-1-benzopyran, the benzopyran (XXIV), described above, is first hydrogenated in the presence of 5% palladium on carbon in ethanol. The so-prepared 8-amino-3,4-dihydro-7-fluoro-2H-1-benzopyran (XXVI) is then optionally halogenated in the 5-position, affording the desired 8-amino-5-chloro-3,4-dihydro-7-fluoro-2H-1-benzopyran (XXVII). Examples 13 and 14 provide detailed descriptions of how these compounds are prepared.

Provenance & Evidence