Urea
SMARTS: [N;$(N-[#6]):3]=[C;$(C=O):1].[N;$(N[#6]);!$(N=*);!$([N-]);!$(N#*);!$([ND3]);!$([ND4]);!$(N[O,N]);!$(N[C,S]=[S,O,N]):2]>>[N:3]-[C:1]-[N+0:2]
Conditions
Reactant 1: isocyanate.
Reactant 2: primary or secondary amine.
R1, R2, R3: aryl, alkyl.
Other sources
Organic chemistry