0000000000138939
AUTHOR
A. Hamdach
Experimental and theoretical DFT study of the reaction of 3-amino-1,2-diols with dichloromethane and paraformaldehyde
Abstract The reactions of 3-phenyl-3-methylamino-1,2-propanediol 1a and 3-[(tert-butyldimethylsilyl)oxy]-1-methylamino-1-phenyl-2-propanol 1b 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 1b with (CH2O)n or CH2Cl2, affords the oxazolidine 2b 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 3b under thermodynamic control. The mechanism proposed for this transformation and the effect of polar solvents on the acceleration of the reactio…
Quantitative ring contraction of 5-hydroxy-1,3-oxazin-2-ones into 5-hydroxymethyl-1,3-oxazolidin-2-ones: A DFT study
Abstract The ring contraction of trans -5-hydroxy-1,3-oxazin-2-ones 1 into cis -5-hydroxymethyl-oxazolidinones 3 was studied with different bases and nucleophiles and it was found that it is the basicity and not the nucleophilicity the factor responsible for the ring contractions. A DFT study was made for the proposed mechanism.
Reactivity difference between diphosgene and phosgene in reaction with (2,3-anti)-3-amino-1,2-diols
In reactions of (2,3-anti)-3-amino-1,2-diols with diphosgene and phosgene and their conversion into 1,3-oxazolidin-2-ones, some differences in the stereochemistry of the reactions have been found with these two reagents. The reactions with phosgene afforded the expected cis-oxazolidinones, and in the reaction with diphosgene under the same reaction conditions, the trans-oxazolidinones were also obtained.
Novel examples of the N-methyl effect on cyclisations of N-Boc derivatives of amino alcohols. A theoretical study
New examples of the N-methyl effect on the cyclisation of N-tert-butoxycarbonyl derivatives of amino alcohols are reported. Ab initio studies for the displacement step with formation of the five-membered heterocycle indicate that the increase of the nucleophile character of the carbonyl oxygen of the carbamate group with the N-methyl substitution is responsible for the acceleration of the cyclisation step.