Jozsef Czombos

Isomerization and hydrogenolysis of 1,3-dioxacycloalkanes on metal catalysts

The isomerization of 5-, 6-, and 7-membered 1,3-dioxacycloalkanes to esters on various metal catalysts is reported, the hydrogenolysis pattern for this type of compound is determined, and a new reaction mechanism is proposed to interpret these catalytic processes.

Configurations and conformations of isomeric 3-methyl-2,4-dioxabicyclo [3.3.1]nonanes - their preparation and multinuclear and 2d nmr study

Abstract Both 3α- ( 1 ) and 3 β-methyl-2,4-dioxabicyclo[3.3.1] nonanes ( 2 ) have been prepared and their configurations and conformations clarified with the aid of high-field 1H, 13C, and 17O NMR study. The β-isomer ( 2 ) was obtained by isomerizing the α-isomer ( 1 ) on Kieselguhr in the gas phase. At 400 MHz in C6D6 all of the 1H signals for 1 ,and 2 could be detected. For the assignment of the 1H and 13C signals heteronuclear shift correlated 2D measurements were used. The vicinal and several long-range coupling constants which were determined with the aid of homonuclear 1H-1H shift correlations (COSY) and several decoupling experiments allowed together with some NOE and ASIS effects as well as with some other NMR data the unambiguous deduction of the configurations and conformations of 1 and 2 .

Hydroisomerization of 1,3-dioxacycloalkanes to esters on platinum. The role of hydrogen in the isomerization

Experiments show that the isomerization of 1,3-dioxacycloalkanes to esters proceeds only in the °presence of hydrogen, and the selectivity for ester formation can be >90% with optimum hydrogen coverage; new data are reported relevant to the mechanism of ester formation and the generalization of the hydroisomerization.