O-Xylene → 1,5-Diazabicyclo(5,4,0)undec-5-ene

Participants

Reaction Steps

The formula (XXXVI) 2-(2-imidazolin-2-yl)quinolinecarboxylate esters can also be prepared from a formula (XXXVIII) dioxopyrroloquinoline acetamide, wherein R1, R2, X, L, M, Q and R7 are as described above, by cyclization thereof with a strong base, such as 1,5-diazabicyclo[5.4.0]undec-5-ene (DBU) in the presence of an inert organic solvent such as xylene or toluene to give the crude imidazopyrroloquinolinedione of formula (XXXVII). The reaction mixture is heated to a temperature between 100° C. and 150° C., and water removed from the reaction mixture using a Dean-Stark water separator. At least one equivalent of alcohol R3OH represented by formula (V); wherein R3 is a substituent as described above, but excluding hydrogen and salt-forming cations, is then added to the reaction mixture, and the thus prepared mixture heated to a reflux at a temperature between 100° C. and 150° C. to yield the formula (XXXVI) ester. The reaction may be graphically illustrated as follows: ##STR35## wherein R1, R2, R3, X, L, M, Q and R7 are as described above.

Provenance & Evidence