Chemical Transformation of the Synthesized 1,2-Dioxane Derivatives

1,2-Dioxan-3-ols can be converted into various functionalized heterocyclic compounds (Scheme 32). For example, the acid-catalyzed decomposition of the 6,6-disubstituted 1,2-dioxan-3-ols quantitatively gave the 2,3,5-trisubstituted furans [78-82]. The reaction could be accounted for as the consequence of an oxygen-oxygen bond cleavage by acid and the migration of a phenyl group at the C-6 position, followed by cyclization and elimination of a phenol. The migratory aptitude was in the order 4-MeOC6H4 > 4-MeC6H4 > Ph = 4-FC6H4 > 4-ClC6H4 = 4-BrC6H4, which was found from the competitive phenyl migration in the reaction of 1,2-dioxan-3-ols bearing two different substituents at the C-6 position.

Treatment of the 4-acetyl-1,2-dioxan-3-ols with alkali resulted in the deacetylated 1,2-dioxan-3-ols via the retro-Claisen condensation by hydroxide ion followed by recyclization [79].

The palladium-catalyzed hydrogenolysis of azabicyclic peroxides led to the formal extrusion of one of the peroxide oxygens and produced the corresponding tetrahydrofuranols in quantitative chemical yields [83,129,174]. The reduction of the 1,2-dioxan-3-ols using triphenylphosphine also afforded tetrahydrofuranols, which were further dehydrated to yield the corresponding dihydrofurans [77].

The hydroxyl group of the 1,2-dioxan-3-ols could be substituted by a methoxyl, acetoxyl, and chloro group [73,167]. The Grignard reaction of the 3-methoxy-1,2-dioxane-4-carboxylates afforded the corresponding alcohols [80]. Further, the 4-bromoacetyl-3-methoxy-1,2-dioxanes could also be converted by the reaction of acetamide, hydrazines, thioureas, thioamides, 4-amino-5-mercapto-1,2,4-triazole, and 2-aminothiophenol into heterocycle-substituted 1,2-dioxane derivatives [167].

Scheme 32 Chemical transformation of the synthesized 1,2-dioxane derivatives
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