FORMATION OF UREA, ISOUREA, AND TRIAZINE DERIVATIVES FROM DIISOPROPYLCYANAMIDE WITH TRIFLUOROACETIC-ANHYDRIDE AND TRIFLUOROMETHANESULFONIC ANHYDRIDE - THERMAL-INSTABILITY OF UREA AND ISOUREA DERIVATIVES
Wp. Norris et al., FORMATION OF UREA, ISOUREA, AND TRIAZINE DERIVATIVES FROM DIISOPROPYLCYANAMIDE WITH TRIFLUOROACETIC-ANHYDRIDE AND TRIFLUOROMETHANESULFONIC ANHYDRIDE - THERMAL-INSTABILITY OF UREA AND ISOUREA DERIVATIVES, Journal of organic chemistry, 62(26), 1997, pp. 9070-9075
Diisopropylcyanamide reacts exothermically with trifluoroacetic anhydr
ide to give 2, an equilibrium mixture, in C6D6 solution, of 1:1 adduct
s, N,N-diisopropyl-N',O-bis(trifluoroacetyl), 2a (10%), and N,N-diisop
ropyl-N',N'-bis(trifluoroacetyl)urea, 2c (90%), at 27 degrees C. Compo
und 2c is a colorless solid, mp 49-51 degrees C. Thermolysis of 2, at
117 degrees C, shows first-order kinetics with the intital products be
ing trifluoroacetonitrile, 4, and diisopropylcarbamic trifluoroacetic
mixed anhydride, 3. Trifluoroacetonitrile trimerizes to 2,4,6-tris(tri
fluoromethyl)-1,3,5-triazine, and 3 is thermally labile giving diisopr
opyltrifluoroacetamide and CO2. In the thermolysis reaction 4 reacts w
ith 2a to give a small amount of toxy)-2,6-bis(trifluoromethyl)-4H-1,3
,5-oxadiazine 7. A related compound, ino)-2,6-bis(trifluoromethyl)-4H-
1,3-5-oxadiazine, 8, is formed from 7 and 2c going through a concentra
tion maximum at 4000 s in the kinetic run. Compound 8 thermolytically
dissociates to generate 4 and tetraisopropylurea. Compound 2 is a tirf
luoroacetylating agent with methanol giving methyl trifluoroacetate in
97% yield. Accompanying this reaction is a methanol displacement of d
iisopropylamine giving a 1.7% yield of methyl-N-(trifluoroacetyl)ureth
ane. Diisopropylcyanamide also reacts exothermically with trifluoromet
hanesulfonic anhydride to give ropylamino)-1-(trifluoromethanesulfonyl
)triazinium trifluoromethanesulfonate, 15, in 96% yield. X-ray crystal
lographic structure drawing of 15 shows N1 (attached to CF3SO2) is pyr
amidal while N2, N4, and N6 (all diisopropylamino nitrogens) are sp(2)
-planar. A small amount of N-diisopropyl-N'-(trifluoromethanesulfonyl)
isourea was also recovered, produced by the reaction of the initially
formed intermediate, opropyl-N',O-bis(trifluoromethanesulfonyl)isourea
, with ethanol contaminant in absolute ethyl ether solvent. Treatment
of 15 with methanol, in the presence of K2CO3, gave a 90% yield of oro
methanesulfonyl)-4-methoxy-1,4-dihydrotriazine.