“…Urea-based catalysts are known to work in such reactions by hydrogen bonding catalysis. 39 On the bases of the results previously discussed, a possible mechanism for the formation of the 1,3-dinitropropane derivative can be postulated, as in Scheme 4. The first step, the formation of nitroaldol, occurs through a classical activation of nitromethane by coordination of the nitro group with urea, promoting the reaction and give betanitro alcohol compound (Scheme 4).…”