Experimental and theoretical DFT study of the reaction of 3-amino-1,2-diols with dichloromethane and paraformaldehyde

The reactions of 3-phenyl-3-methylamino-1,2-propanediol and 3-[(tert-butyldimethylsilyl)oxy]-1-methylamino-1-phenyl-2-propanol with (CH2O)n and CH2Cl2 are appropriate procedures for the preparation of 1,3-oxazines or 1,3-oxazolidines under proper selection of kinetic or thermodynamic reaction conditions. The reaction of with (CH2O)n or CH2Cl2, affords the oxazolidine under kinetic conditions and then this compound can be slowly converted into 5-[(tert-butyldimethylsilyl)oxy]-3-methyl-4-phenyl-3,4,5,6-tetrahydro-2H-1,3-oxazine under thermodynamic control. The mechanism proposed for this transformation and the effect of polar solvents on the acceleration of the reaction has been studied theoretically (DFT level).