Production method for 3,3-dimethyl-3,4-dihydro-1h-quinoxalin-2-one derivative and intermediate for said production method

A method for producing a compound represented by formula (2):

• wherein R1 represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group,
• R2 represents a hydrogen atom, an alkyl group, a hydroxy group, or a t-butoxycarbonyl group,
• R4 represents an alkyl group, a cycloalkyl group, or an aryl group, and
• X represents a hydroxy group or a halogen atom,
• or a salt thereof, the method comprising the step of reacting a compound represented by formula (4):
• wherein R1, R2, and X are the same as defined in formula (2),
• or a salt thereof with a compound represented by formula (5′):
• wherein R4 is the same as defined in formula (2), and
• Y represents a hydroxy group or a halogen atom,
• or a salt thereof to obtain the compound represented by formula (2) or the salt thereof.

A compound represented by formula (2) or a salt thereof:

• wherein R1 represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group,
• R2 represents a hydrogen atom, an alkyl group, a hydroxy group, or a t-butoxycarbonyl group,
• R4 represents an alkyl group, a cycloalkyl group, or an aryl group, and
• X represents a hydroxy group or a halogen atom.

A method for producing a compound represented by formula (8):

• wherein R1 represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group,
• R2 represents a hydrogen atom, an alkyl group, a hydroxy group, or a t-butoxycarbonyl group, and
• R3 represents a hydrogen atom, an optionally substituted alkyl group, a hydroxy group, or a nitrogen atom-protecting group,
• or a salt thereof, the method comprising the step of reacting a compound represented by formula (9):
• wherein R1, R2, and R3 are the same as defined in formula (8),
• or a salt thereof with a compound represented by formula (5″):
• wherein R5 represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group, and
• Y represents a hydroxy group or a halogen atom,
• or a salt thereof to obtain the compound represented by formula (8) or the salt thereof.