Dibenzyl carbonate

Alpha -Nitro-Alpha-lmino-Dibenzyl-Carbonic... 

Dibenzoyltartaric anhydride, chiral derivatizing reagent, 6 76t Dibenzylamine, 3 595 Dibenzyl carbonate, molecular formula, 6 305t... 

In 1998, Gan and Takeuchi identified a key role of anode surface him composition in SVO cell performance [64], The addition of carbon dioxide synthons such as dibenzyl carbonate and benzyl succinimidyl carbonate was found to reduce resistance build-up and alleviate voltage delay in silver vanadium oxide cells. 

Alphe -Nitro-Alpha-lmino-Dibenzyl-Carbonic acid-2. C,sHi2N204,C6Hs.CH(N02).C( NH). C6H4.CO2H, mw 284.29, N 9.86%, OB to CO2 —180.10%, sulfur-yel cryst, mp 147—150° (decompn). Prepd by warming alpha-nitro-benzal-phthalimidin with dil aq NaOH Ref 1) Bed 10, 757... 

Dibenzyl carbonate, Pb4PBr, 150-170°C, neat, 76-93% yield. These conditions give dibenzyl amines with only minimal amounts of the carbamates. ... 

Dibenzyl carbonate, ionic liquid, DABCO, CH3CN, 85°C, 23 h, 28-93% yield. This method has also been used to methylate indoles in excellent yield by using dimethylcarbonate. ... 

Ionic liquids have been reported to accelerate slow AT-benzylation reactions of benzimidazole 65 utilizing dibenzyl carbonate 66 as an alkylating reagent (Scheme 13) [55]. An additional rate enhancement was observed when microwave irradiation was applied in this reaction to afford the N-benzylbenzimidazole 67. 

In 2008, BackvalFs group employed a closely related methodology for the production of benzyl carbamates, allowing a further release of the free amines under very mild conditions. Indeed, a drawback with other DKR procedures of amines is that the product is a chiral amide, from which the free amine can only be liberated under harsh reaction conditions. As shown in Scheme 4.43, a series of amines could be converted through DKR in the presence of dibenzyl carbonate as the acyl donor into the corresponding carbamates in both excellent yields and enantioselectivities. In this case, CAL-B was associated with Shvo s catalyst. 

Iwashige, T. et al. Chem. Pharm. Bull, 1967, 15, 132 1968, 16, 1040 (carbonate, benzyl carbonate, dibenzyl carbonate, dibenzyl, dibenzyl mesyl trityl)... 

Typical procedure. Dibenzyl carbonate 981 [708] To a stirred solution of benzyl alcohol (0.216 g, 2.00 mol), tributylphosphine (0.303 g, 1.50 mmol), and CyTMG (0.394 g, 2.00 mmol) in DMF (2.00 mL), CO2 was added at room temperature. After 15 min, tetrabromomethane (0.663 g, 2.00 mmol) was added, the reaction vessel was sealed, and the contents were stirred for 2 h. Thereafter, the reaction mixture was diluted with ethyl acetate, washed successively with 0.5 m aqueous HCl and saturated aq. NaHCOs solution, and dried over Na2S04. Diphenyhnetha-... 

Electrolyte additives, such as an organic carbonate like dibenzyl carbonate (DBG), have a signiflcant impact on the long-term performance of Li-AgV02 batteries. In addition, this electrolyte additive reduces the internal resistance by modifying the surface layer at the lithium anode. 

Electrolytes which have been employed with this system are 1 molar LiBp4 in propylene carbonate (PC) and 1 Molar LiAsFg in 1 1 by volume PC-DME. The latter appears to be the electrolyte of choice at present. The addition of CO2 or substances such as dibenzyl carbonate (DBC) or benzyl succinimidyl carbonate have been reported to reduce anode passivation which causes voltage delay and increased DC resistance between 40 and 70% depth of discharge." These materials are believed to operate by lowering the impedance of the solid electrolyte interface (SEI) layer on the surface of the lithium anode. 

The substrate scope of the DKR protocol above was extended to include a wide range of primary amines [89]. Functional groups tolerated include fluorine, bromine, nitrile, nitrate, and trifluoromethyl. Aliphatic amines and more sterically hindered substrates were also obtained in high yields and ee values. The method was found applicable with both isopropenyl acetate and dibenzyl carbonate as acyl donors. For 18 different substrates, the corresponding enantiomericafly pure products were obtained in high to excellent yields (70-95%) and with high to excellent ee values (93 to >99%). The chemoenzymatic DKR protocol was also applied to the synthesis of norsertraline, from readily available 1,2,3,4-tetrahydro-l-naphthyl-amine. Norsertraline is cmrently in clinical trials for the treatment of central nervous system (CNS) disorders. 

The previous DKR procedures employing alkyl acetates as the acyl donors had a limitation that the deacylation of products to obtain free amines required a harsh conditions. This limitation was avoided by using dibenzyl carbonate as the acyl donor (Scheme 5.32 and Chart 5.31). The benzyloxycarbonyl group of the product was readily removed by Pd-catalyzed hydrogenolysis [55]. 

DKR of primary amines using dibenzyl carbonate as the acyl donor. 

Backvall and coworkers have also developed a practical method for the chemo-enz3unatic DKR of primary amines using dibenzyl carbonate as acyl donor, combining the use of CAL-B and the ruthenium complex mentioned above in toluene at 90 °C for the production of enantioenriched (R)-carbamates (60-95% )deld, 90-99% ee Table 9.6) [243]. The main advantage of this method is that the benzyloxycarbonyl group (Cbz) can be easily removed by hydrogenolytic cleavage without any loss of the carbamate optical purity (compoimd in entry 1 of Table 9.6) [244]. 

TABLE 9.6 DKR of Primary Amines with 2.5 Equivalents of Dibenzyl Carbonate Catalyzed by CAL-B and 4mol% of a Ruthenium Catalyst in the Presence of Na CO ... 

Application of a Shvo s type Ru-catalyst in combination with C. Antarctica lipase B was enabled to perform the DKR of a number of functionalized primary amines to produce in high yields, the corresponding acetates almost as single enantiomers using isopropyl acetate or dibenzyl carbonate as the acyl donor. 

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