Di-a-pyridyl carbonate

A soln. of 4-chlorophenyl phosphate, triethylamine, and di-a-pyridyl carbonate in abs. acetonitrile kept overnight at 60°, the crude intermediate a-pyridyl phosphate treated with phenyl phosphate in pyridine, and the product isolated as the cyclohexylammonium salt after 6-8 hrs. at room temp. P -phenyl P2-4-chlorophenyl diphosphate. Y 88.4%. F. e. and reactions of -pyridyl phosphates s. W. Kampe, B. 98, 1038 (1965) nucleoside diphosphoric acids s. B. 98, 1045 from a-pyridone instead of di-a-pyridyl carbonate cf. B. 99, 593 (1966). 

Pyridyl methacrylate has been prepared from the sodium salt of 2-pyridone and methacryl chloride and has been polymerized by radicals but not by anions. 2-Pyridone and phosgene (1 4) in dry tetrahydrofuran or benzene with or without pyridine form di-(a-pyridyl)carbonate, which is a useful reagent for the formation of the benzoate and the monophenyl phosphate of 2-pyridone. ... 

Pyridyl-3-butyrolactonyl ketones, conversion to quin-olizinaS/ 355 2-Fyridyl carbinols, 19 Di (a-pyridyl) carbonate, prepared from 2-pyridone and phosgene, 777, 781 2-Pyridylcinnamic acid, ethyl ester, preparation from ethyl pyridyl acetates, 344 stereochemistry of, 344 a-Pyridylcinnamic acids, decarboxylation to stilba-zoles, 340, 349... 

Carbon suboxide (C,HfikCO Di-a-pyridyl carbonate Oxime carbonates (30) CO2... 

A. K. Ghosh, T. T. Duong, and S. P. McKee, Di(2-pyridyl) carbonate promoted alkoxycar-bonylation of amines A convenient synthesis of functionalized carbamates. Tetrahedron Lett. 32 4251 (1991). 

Polymer-bound reagents have also been used. The synthetically important Weinreb amides [RCON(Me)OMe, see 16-82] can be prepared from the carboxylic acid and MeO(Me)NH HCl in the presence of tributylphosphine and 2-pyridine-A -oxide disulfide. Di(2-pyridyl)carbonate has been used in a related reaction that generates amides directly. The reaction of a carboxylic acid and imidazole under microwave irradiation gives the amide. Microwave irradiation of a secondary amine, formic acid, 2-chloro-4,6-dimethoxy[l,3,5]tria-zine, and a catalytic amount of DMAP (4-dimethylaminopyridine) leads to the formamide. ° Ammonium bicarbonate and formamide converts acids to amides with microwave irradiation. Lactams are readily produced from y- or 8-amino acids, for example. 

DCC-DMAP has been used in the synthesis of depsipeptides. Macrocyclic lactones have been prepared by cyclization of hydroxy carboxylic acids with DCC-DMAP. The presence of salts of DMAP, such as its trifluoroacetate, is beneficial in such cyclizations, as shown for the synthesis of a (9. -dihydroerythronolide. Other macrolactonizations have been achieved using 2,4,6-Trichlorobenzoyl Chloride and DMAP in Triethylamine at rt or Di-2-pyridyl Carbonate (6 equiv) with 2 equiv of DMAP at 73 °C. ... 

The reaction of di(2-pyridyl) carbonate (DPC) 725 with a variety of alcohols, including hindered secondary, tertiary, and protected glycols, afforded the corresponding mixed carbonates, which were efficiently transformed into various carbamates in high yield under mild conditions. DPC is quite stable and can be stored at room temperature for several months without any noticeable decomposition. This method has allowed the preparation of a variety of functionalized carbamates (Table 4.24), overcoming many of the limitations associated with the alkoxycar-bonylation methodologies [505]. 

A versatile reagent for a convenient synthesis of various functionalized carbamates (see Section 4.3.2), ureas, interchanged carbonates, and active esters for activation in forming peptide bonds, as well as for the direct esterification of carboxylic acids [635-637] (see also Section 4.3.3.7), is di-2-pyridyl carbonate, DPC, 725. It is prepared from commercially available 2-hydroxypyridine and phosgene in 90% yield [638]. 

Typical procedure. Di-2-pyridyl carbonate, DPC, 725 [638] A solution of phosgene (for a safe source, see Chapter 7) (2.5 m in toluene, 2 mL, 5.0 mmol) was diluted with dichloromethane (8 mL) and then a solution of 2-pyridinol 853 (950 mg, 10 mmol) and triethylamine (1.214 g, 10.2 mmol) in dichloromethane (20 mL) was added at 0 °C. The reaction mixture was stirred at 0 °C for 1 h, then washed with cold 5% NaHCOs solution (20 mL) and cold saturated brine (20 mL), dried over MgS04, and filtered. The filtrate was concentrated to dryness to give di-2-pyridyl carbonate, DPC, 725 (972 mg) in 90% yield. It was recrystallized from dichloro-methane/petroleum ether (811 mg, 75%) mp 84—86 °C. 

Typical procedure. Di-2-pyridyl carbonate hydrochloride, DPC-HCI, 877 [639] Avoid sunlight (2-hydroxypyridine is light-sensitive) and work in a well-ventilated fUmehood. In a 2-L three-necked flask equipped with a gas inlet tube, stirrer, and reflux condenser, 2-hydroxypyridine 724 (47.5 g, 500 mmol) was dissolved in absolute THF (750 mL) with stirring and mild warming. Phosgene (for a safe source, see Chapter 7) (12.4 g, 8.9 mL, 125 mmol) was passed into the solution, and then nitrogen was... 

The reagent 1292 can be conveniently prepared in 94% yield by the addition of N,0-dimethylhydroxylamine hydrochloride 1291 and triethylamine to a solution of di-2-pyridyl carbonate (DPC) in dichloromethane at 0 °C. It is easily separated by aqueous work-up (2-hydroxypyridine is very soluble in water) and purified by column chromatography on silica gel or kugelrohr vacuum distillation (bp 116-120 °C/0.20 mmHg). This phosgene equivalent shows no sign of decomposition when kept for two months in a refrigerator. 

Typical procedure. p-Methoxyvalerophenone 1294k [963] Preparation of N-Methoxy-N-methyI-2-pyridyI urethane 1292 To a solution of di-2-pyridyl carbonate (2.162 g, 10 mmol) in dichloromethane (30 mL), N,0-dimethylhydroxylamine hydrochloride 1289 (975.5 mg, 10 mmol) and triethylamine (1.42 mL, 10.2 mmol) were added at 0 °C. After stirring for 1 h at 0 °C, the reaction mixture was allowed to warm to room temperature over a period of 1 h. It was then poured into saturated aq. NaHCOj solution (60 mL) and the aqueous phase was extracted with dichloromethane (3 X 30 mL). The combined organic extracts were dried over MgS04, filtered, and concentrated to dryness in vacuo. The crude product was purified by... 

The preparation of mixed carbonates and their transformaticMi to fiinctionaUzed carbamates by use of di(2-pyridyl) carbonate has been reported. A caibdiydrate example is given in Scheme 12. ... 

A similar approach was taken for the synthesis of 45 by Miyaura. " Shaughnessy and Booth synthesized the water-soluble alkylphosphine 46, and found it to provide very active palladium catalysts for the reaction of aryl bromides or chlorides with boronic acids. The more sterically demanding ligand 47 was shown to promote the reactions of aryl chlorides with better results than 46. Najera and co-workers recently reported on the synthesis of di(2-pyridyl)-methylamine-palladium dichloride complexes 48a and 48b, and their use in the coupling of a variety of electrophiles (aryl bromides or chlorides, allyl chlorides, acetates or carbonates) with alkyl- or arylboronic acids very low catalyst loadings at Palladium-oxime catalysts 8a and 8b) have also been developed. In conjunction with... 

Finally, a recently reported copper catalyzed carbon-nitrogen bond forming process utilises reagents with polarity opposite to the common disconnection protocols. An electrophilic nitrogen, in most cases an (9-acyl hydroxylamine derivative, was successfully coupled with diarylzinc reagents in the presence of copper triflate or copper chloride. Di(2 -pyridyl)zinc and TV-benzoyloxy-morpholine were reacted at ambient temperature in the presence of 1% copper(I) triflate to give 2-morpholinopyridine in 71% yield (7.81.), Under these mild conditions the reaction was over in less than one hour.103... 

Reaction of the l,5-diphenyl-3-(2-pyridyl)pentane-l,5-dione 47 with 2.5equiv of benzylpentacarbonylmanganese in petroleum under reflux gave a small amount of the symmetrical di-aryl-manganated product 48 but mostly the complex 49, which is manganated at only one aryl carbon (by Mn(CO)4) but also (by Mn(CO)3 with N- and O-coordination) at the methylene carbon adjacent to the Mn(CO)4-coordinated ketone carbonyl (Scheme 6). The latter is a rare example of direct cyclomanganation at a saturated carbon and the only known case adjacent to carbonyl <2005JOM3348>. 

Trimethylene-2,2 -bi-l,8-naphthyridine with [Re(CO)5Br] in heptane gives the bidentately coordinated complex 27 (960M3463). Compounds of the same composition, [Re(CO)3(LL)Cl] (LL = 3,3,-dimethylene-2,2,-biquinoline) can be prepared similarly (94IC2341). / -(2,6-di-2-pyridyl-4-pyridyl)phenol reacts with [Re(CO)5Cl] and forms complex 28 with bidentate coordination of the ligand (92JPP(A)259). The product is active in the electro- and photochemical reduction of carbon dioxide. Species [Re(CO)3(2,7-bis(2,-pyridyl)-l,8-naphthyridine)Br] is known (83ICA(76)L29). 

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