Phenylurethane compounds and methods for producing same, asymmetric urea compounds and methods for producing same, barbituric acid derivative, and diazo thermal recording material containing the derivative

A barbituric acid derivative having a molecular structure corresponding to the following general formula (21):

• wherein R3 represents a hydrogen atom, an optionally-substituted alkyl group, or an optionally-substituted aralkyl group;
• R4 represents an optionally-substituted alkyl group or an optionally-substituted aralkyl group;
• R3 is independent of R4;
• R5 represents a hydrogen atom, an optionally-substituted alkyl group, or an optionally-substituted aralkyl group;
• R6 represents an optionally-substituted alkyl group, or an optionally-substituted aralkyl group;
• R5 is independent of R6;
• and L is selected from the group consisting of a hydrogen atom, a halogen atom, alkoxy group, an aryloxy group, an acyloxy group, an alkyl or arylsulfonyloxy group, an acylamino group, an alkyl or arylsylfonamido group, an alkoxycarbonyloxy group, an aryloxycarbonyloxy group, an alkyl, aryl or heterocyclic group, a carbamoylamino group, an arylsulfinyl group, an arylsulfonyl group, a 5-membered or 6-membered nitrogen-containing heterocyclic group, an imido group, an arylazo group, an amino group, an ether group or a thioether group and wherein the substituent bonded to one nitrogen atom shown in general formula (21) is different from the substituent bonded to the other nitrogen atom.