Processes for fractionation of biomass

A method of processing biomass comprising heating a mixture comprising biomass and a solvent comprising a compound of Formula (1):

• wherein
• R1 is selected from C1-8alkyl, C3-8cycloalkyl, aryl, or C1-8heteroaryl optionally substituted one or more times by F, Cl, Br, C1-8alkoxy, C3-8cycloalkyl, aryl, C1-8heterocyclyl, or C1-8heteroaryl;
• R3 is selected from H, C1-8alkyl, C3-8cycloalkyl, aryl, or C1-8heteroaryl optionally substituted one or more times by F, Cl, Br, C1-8alkoxy, C3-8cycloalkyl, aryl, C1-8heterocyclyl, or C1-8heteroaryl;
• R2 and R2* together form an oxo, or
• R2* is H and R2 is OR2a wherein R2a is selected from H, C1-8alkyl, C3-8cycloalkyl, aryl, or C1-8heteroaryl optionally substituted one or more times by F, Cl, Br, C1-8alkoxy, C3-8cycloalkyl, aryl, C1-8heterocyclyl, or C1-8heteroaryl.