N-tert-butoxycarbonyl-2-pyrrolidinones and production method thereof

N-tert-butoxycarbonyl-2-pyrrolidinones represented by the following formula (1). In the formula (1), R1, R2, R3, R4, R5 and R6 independently represent a hydrogen atom, a halogen atom, a cyano group, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, which may have a substituent, a linear, branched or cyclic alkenyl group having 2 to 10 carbon atoms, which may have a substituent, or the like, R1 and R2 may be linked to form a >C O group along with the carbon atom to which both are attached, R3 and R4 may be linked to form a >C O group along with the carbon atom to which both are attached, R5 and R6 may be linked to form a >C O group along with the carbon atom to which both are attached, or any two among R1, R2, R3, R4, R5 and R6 may be linked to form a polymethylene group having 1 to 4 carbon atoms which may have a substituent.