Trioxane aldol reaction

Formaldehyde-MAPH complexesFormaldehyde (gas) readily undergoes self-polymerization and is usually generated by thermal depolymerizaton of paraformaldehyde, a linear trimer. Treatment of trioxane in CH2C12 at 0° with MAPH generates a complex, CH2=O MAPH, which is stable at 0° for 5 hours, but which decomposes slowly at 25°. The complex can be used for aldol and ene reactions of the aldehyde itself. 

In a typical synthesis, a mixture of C13H12O2 bisphenols was prepared in 80% yield by slow addition of a solution of trioxane (0.036 mole) in benzene (over 1.75 hour) to a stirred, liquid phase suspension of phenol (0.64 mole) and HY zeolite (5 gm) at 182°. The ratio of the 2,2, 2,4, and 4,4 isomers was 1.3 1.8 1.0. This technique, which afforded very high instantaneous ratios of phenol to aldehyde, prevented rapid catalyst aging. Generally, high yields were observed for carbonyl reactants with no a-hydrogens, since competitive intracrystalline aldol condensation reactions were eliminated. 

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