Catalytic oxidative carbonylation of primary and secondary diamines to cyclic ureas. Optimization and substituent studies.
W(CO)(6)-catalyzed oxidative carbonylation of 1,3-propanediamine to the corresponding urea has been examined under a variety of conditions. Following optimization, the Thorpe-Ingold effect on ring closure was studied using 2,2-dialkyl-1,3-propanediamines. For the 2,2-dimethyl- and 2,2-dibutyl-1,3-propanediamines, the yields were increased significantly as compared to that of the unsubstituted case. The eight-membered cyclic urea 5-butyl-5-ethyl-1,3-diazepan-2-one (5f) was formed in 38% yield, while only trace amounts of the cyclic urea were produced from the parent 1,5-pentanediamine. In a study of secondary diamines, yields from the carbonylation of N,N'-dialkyl-2,2-dimethyl-1,3-propanediamines were lower than those obtained from the primary diamines. The main byproducts from secondary diamines were tetrahydropyrimidine derivatives formed from a competitive reaction of the substrate with the oxidant and base.
Qian
Fang
F
Department of Chemistry and Center for Catalysis, University of Florida, Gainesville 32611-7200, USA.
McCusker
Jennifer E
JE
Zhang
Yue
Y
Main
A Denise
AD
Chlebowski
Mary
M
Kokka
Michiyo
M
McElwee-White
Lisa
L