Lawesson's reagent → 5,11-dihydro-11-ethyl-5-methyl-6H-dipyrido[3,2-b:2', 3'-e][1,4]diazepin-6-thione
Reaction equation
[CH2:1]([N:3]1[C:9]2[N:10]=[CH:11][CH:12]=[CH:13][C:8]=2[C:7](=O)[N:6]([CH3:15])[C:5]2[CH:16]=[CH:17][CH:18]=[N:19][C:4]1=2)[CH3:2].COC1C=CC(P2(SP(C3C=CC(OC)=CC=3)(=S)S2)=[S:29])=CC=1>C1(C)C=CC=CC=1>[CH2:1]([N:3]1[C:9]2[N:10]=[CH:11][CH:12]=[CH:13][C:8]=2[C:7](=[S:29])[N:6]([CH3:15])[C:5]2[CH:16]=[CH:17][CH:18]=[N:19][C:4]1=2)[CH3:2]Participants
4
Procedure
A mixture of 2.66 g (0.01 mol) of 5,11-dihydro-11-ethyl-5-methyl-6H-dipyrido-[3,2-b:2'3'-e][1,4]diazepin-6-one and 2.10 g (0.005 mol) of Lawesson's reagent (2,4-bis(4-methoxyphenyl)-1,3-dithia-2,4-diphosphetane-2,4-disulfide) in 50 ml of toluene was refluxed for 2 1/2 h. The solvent was then removed in vacuo and water was added to the residue. The product was extracted with ethyl acetate, dried (anhydrous sodium sulfate), and concentrated in vacuo. Purification was effected on a silica gel column using methylene chloride as the first eluent, followed by ethyl acetate/hexane (1:4). Removal of the solvent in vacuo gave 2.20 g (74% of theory) of 5,11-dihydro-11-ethyl-5-methyl-6H-dipyrido[3,2-b:2', 3'-e][1,4]diazepin-6-thione as a yellow powder, which was recrystallized from 10% hexane/ethyl acetate to provide 1.1 g of the title compound as yellow needles, m.p. 157°-158° C.