The t i t b compound I rcacts with alkyl (or phenyl) isocyanates 2 in a molar ratio of 1 : t to give the N-monoadducts 3 which cyclim readily to yield the 6-aminouracils 4, whereas in a molar ratio of 1 : 1 mainly N.N-bisadducts 6 and. in LWO cases, small amounts of C.N-bisaadductr 5 are lormcd. The N.N-bisadducrs 6 are extremely sensitive 10 water giving the ureido esters 7. but can bc mnvcrtcd into substituted uracils 8 under basic conditions. The addition of I to isothiocyanates 9 yiclds mainly the C-monoadducts 10 and. as minor products, thc 6-amino-2-thiouracils 11.
Enamino compounds with a tertiary amino group add to heterocumulenes giving exclusively C-carbamoylated derivatives, whereas those with a primary or secondary amino group can lead to either Cor N-adducts". The readily available alkyl 3-aminocrotonates provide N-adducts which cyclize to give 6-methyluracils in the presence of a base2). Similarly, the 3-alkoxy-3-aminopropenoic esters add to organic isocyanates or isothiocyanates yielding initially N-adducts which are cyclized to yield 6-alkoxyuracils ' ' .
Ethyl 3,3-diaminopropenoate4) (1) possesses three nucleophilic centres (N,N' and C-2) in its molecule and therefore its reactivity towards heterocumulenes could not be predicted. In a preliminary communication') we described the reaction of 1 with phenyl isocyanate (2f) and isothiocyanate (9e) leading to compound 3f, 6f, and 10e. A more detailed study on the addition of 1 to isocyanates and isothiocyanales, including some properties of the formed adducts, is reported in this paper. Scheme 1 3a-f ha-f 2 -4 1 a b c d e f
Thus, the reaction of 1 with the isocyanates 2a-f in a molar ratio of 1: 1 (Scheme 1) proceeded in acetonitrile at room temperature within 1-3 d (TLC control). The crystalline N-monoadducts 3a and f were isolated in good yields.