1,4-dimethylpiperazine-2,3-dione

Conditions: temp:-78.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of 4-bromobenzaldehyde diethyl acetal (20.05 g, 77.4 mmol) in 80 mL of dry THF was added 31 mL of n-BuLi (2.5 M in hexanes, 77.4 mmol) by a syringe at −78° C. After stirring at −78° C. for 1 h, the mixture was transferred to a suspension of 1,4-dimethylpiperazine-2,3-dione (DMPD) (5.0 g, 35.0 mmol) in 80 mL of dry THF dropwise via a cannula under an argon counterflow. The reaction mixture was gradually warmed up to room temperature and stirred at room temperature for an additional 2 h. The mixture was then hydrolyzed with 10% HCl and extracted with CH2Cl2. The organic layer was dried over anhydrous MgSO4 and the solvent was removed under reduced pressure. The product was purified by column chromatography (silica gel, dichloromethane:hexanes=4:1 (v/v)) to give a yellow solid (2.00 g, 21% j. 1H NMR (300 MHz, CDCl3, δ): 10.13 (s, 2H), 8.14 (d, J=8.1 Hz, 4H), 8.02 (d, J=8.8 Hz, 4H). 13C{1H} NMR (75 MHz, CDCl3, δ): 192.41, 191.24, 140.22, 136.60, 130.54, 130.04. HRMS-EI (m/z): [M]+ calcd for C16H10O4, 266.0579; found, 266.0584. Anal. Calcd for C16H8N2O2: C, 72.18; H, 3.79. Found: C, 72.03; H, 3.74. The reaction mixture was gradually warmed up to room temperature stirred at room temperature for an additional 2 h hydrolyzed with 10% HCl and extracted with CH2Cl2 The organic layer was dried over anhydrous MgSO4 the solvent was removed under reduced pressure The product was purified by column chromatography (silica gel, dichloromethane:hexanes=4:1 (v/v)) to give a yellow solid (2.00 g, 21% j

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a stirred solution of N,N′-dimethylethylenediamine (25.0 g, 0.28 mol) in 150 mL of dry diethyl ether was added diethyl oxalate (38.5 mL, 0.28 mol) in one portion. After a few minutes white crystals started to precipitate. The reaction mixture was stirred at room temperature overnight. The product was filtered and washed with dry diethyl ether. The product was dried under vacuum at 47° C. overnight to give colorless crystals (38.64 g, 96%). 1H NMR (200 MHz, CDCl3, δ): 3.50 (s, 4H), 2.99 (s, 6H). 13C{1H} NMR (200 MHz, CDCl3, δ): 157.35, 45.91, 34.74. After a few minutes white crystals started to precipitate The product was filtered washed with dry diethyl ether The product was dried under vacuum at 47° C. overnight

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Mueller-Westerhoff9 and co-workers reported a simple, high-yield two-step synthesis of symmetrically substituted α-diones. The first step involves the preparation of 1,4-dimethylpiperazine-2,3-dione (13). Compound 13 was prepared in high yield from the reaction between N,N′-dimethylethylenediamine and diethyl oxalate in anhydrous diethyl ether at room temperature overnight. Second, compound 13 reacts with 2 equivalents of organolithium or Grignard compounds to form symmetrically-substituted α-diones after hydrolysis. 3,3′-Dimethylbenzil was prepared from the reaction between compound 13 and 2 equivalents of m-tolylmagnesium chloride in dry THF, followed by acidic workup in 35% yield (not optimized). Bis[1,2-di(3-methylphenyl)ethane-1,2-dithiolene]nickel (17) was then prepared by Schrauzer and Mayweg procedure as shown in FIG. 8.10 to form symmetrically-substituted α-diones after hydrolysis

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a suspension of 1,4-dimethylpiperazine-2,3-dione (2.08 g, 1.46×10−2 mol) in 50 ml of dry Et2O was added 3,7-dimethyloctyl lithium (0.45M solution in Et2O, 65 ml, 2.9×10−2 mol, freshly prepared from 3,7-dimethyloctyl bromide and lithium) by a syringe. After 40 min of stirring at room temperature under N2, the solution was hydrolyzed with 100 ml of 10% HCl and extracted with CHCl3. The combined organic layers were washed with saturated aqueous NaHCO3 and dried over Na2SO4. The product was chromatographed on silica gel with 3:1 hexane:CHCl3 as the eluent. Yield=4.446 g (91% based on 65 ml of 0.45M 3,7-dimethyloctyl lithium in Et2O). 1H NMR (250 MHz, CDCl3): δ 2.69-2.78 (m, 4H, —CH2CO), 1.06-1.65 (m, 20H, (CH3)2CHCH2CH2CH2CH(CH3)CH2CH2CO), 0.87 (d, 6H, J=9.0 Hz, —CH3), 0.86 (d, 12H, J=9.5 Hz, —CH3). CI MS m/z: 338.3175 (M+) (calcd 338.318). extracted with CHCl3 The combined organic layers were washed with saturated aqueous NaHCO3 dried over Na2SO4 The product was chromatographed on silica gel with 3:1 hexane