Pyridine triphosgene

Treatment of the 2-amino-3-hydroxypyridine 161 with triphosgene resulted in the formation of the l,3-oxazolo[4,5- ]-pyridin-2(37T)-one 162, an intermediate in the formation of CRF-1 receptor ligands (Equation 59) <2005TL1683>. Oxazolo[4,5-, ]pyridines have been synthesized using a triphenylphosphine-hexachloroethane combination, with the triphenylphosphonium halide being formed prior to addition of the amide (Equation 60) <2005TL9001>. 

Difficult N-acylations, such as those of A-alkylanilines or a-alkylamino acid derivatives, are most conveniently performed with acyl halides in non-nucleophilic solvents (e.g. DCM, DCP) in the presence of pyridine or DIPEA [13]. Acyl halides can be prepared on insoluble supports under conditions similar to those used in solution. Typical reagents for the preparation of acyl chlorides include oxalyl chloride [19-21], thionyl chloride [22,23], and triphosgene [13]. Anhydrous solvents must be used for all wash-... 

Transesterification has been carried out with phase-transfer catalysts, without an added solvent. Nonionic superbases (see p. 365) of the type P(RNCH2CH2)3N catalyze the transesterification of carboxylic acid esters at 25°C. ° Silyl esters (R C02SiR3) have been converted to alkyl esters (R C02R) via reaction with alkyl halides and tetrabutylammonium fluoride. Thioesters are converted to phenolic esters by treatment with triphosgene-pyridine and then phenol. 

Carbamoyl chlorides. A direct preparation of carbamoyl chlorides from tertiary benzylamines (debenzylation) is by reaction with triphosgene. A-Methoxy-N-methyl-carbamoyl chloride, which is useful for coupling with various unsaturated organostannanes, is obtained from chloroformylation of the methoxylamine in the presence of pyridine. ... 

Interestingly, the chloroformate (diphosgene) and the carbonate (triphosgene) react with pyridine to give the same product (see also Chapter 12). The material described as (py)j. jCOClj, prepared from the reaction of phosgene with pyridine in benzene solution, was noted to lose half a molar equivalent of pyridine upon standing over PjOj in vacuo [1809a]. 

Phosgene or triphosgene in the presence of a hase such as TEA or pyridine in CH2CI2 is a common method for oxazolidinone formation. Triphosgene has the advantage that it is an easily handled solid. ... 

Scheme 125. Reagents a, ZnCli, THF, -80°C to 25°C b, aq. NaHCOs, then Si02 c, triphosgene d, LiHMDS, 2-(NTf2)-pyridine, THF, -80°C e, H2 (1 atm.), PtOi, EtOH, rt f, KOBu, THF, 0°C g, (COCl)2, DMSO, EtjN, CH2CI2, -65 C to rt h, Ph3P=CHC02Et, CH2CI2 i, H2 (1 atm.), Pd/C. EtOH j, PhMe, reflux k, LiAlH4, THF, reflux.

Microwave irradiation can be used to make oxazolo[4,5-fc]pyridines and allows reaction with amides in lieu of acids when urea or thiomea are used, 2-ones (2-thiones) are obtained carbon disulfide with potassium hydroxide also leads to 2-thiones. The use of triphosgene and 2,3-diamino-pyridines can be used to made the analogous imidazo[4,5-b]pyridin-2-ones. Reaction with cyanogen bromide gives... 

Anhydrides and cyclic carbonates. Symmetrical anhydrides are formed when acids are treated with (Cl jCOlaCO and Et3N. The transformation of the terminal glycol unit of a 1,2,3-triol to the cyclic carbonate can be accomplished with triphosgene and pyridine on the other hand, the internal diol system is protected using NaH and (MeO)2CO. 

The amides 23, i.e., the products from the reaction of the anhydride (1) and the acetylenic amides 21 (see part 1), undergo cyclization to the derivatives of oxazoloquinazoline 275 (yields 31-50%) when treated with triphosgene in pyridine. The configuration of the initial amines 21 and amides 23 is retained [10],... 

Chloro-, Bromo- and lodo-sugars. - The preparation of glycosyl halides and their use in the solid-phase synthesis of oligosaccharides has been reviewed/ A new method for the preparation of glycosyl chlorides involves the treatment of otherwise protected free sugars with triphosgene in the presence of pyridine/ ... 

Related Reagents. Dimethyl Sulfoxide-Acetic Anhydride Dimethyl Sulfoxide-Dicyclohexylcarbodiimide Dimethyl Sulfoxide-Methanesulfonic Anhydride Dimethyl Sulfoxide-Oxalyl Chloride Dimethyl Sulfoxide-Phosgene Dimethyl Sulfoxide-Phosphorus Pentoxide Dimethyl Sulfoxide-Sulfur Trioxide/Pyridine Dimethyl Sulfoxide-Tiifluoroacetic Anhydride Dimethyl Sulfoxide-Triphosgene. 

Related Reagents. A/-Chlorosuccinimide-Dimethyl Sulfide Chromic Acid Dimethyl Sulfide-Chlorine Dimethyl Sulfoxide-Acetic Anhydride Dimethyl Sulfoxide-Dicyclo-hexylcarbodiimide Dimethyl Sulfoxide-Oxalyl Chloride Dimethyl Sulfoxide-Phosphorus Pentoxide Dimethyl Sulfoxide-Sulfur Trioxide/Pyridine Dimethyl Sulfoxide-Trifluoroacetic Anhydride Dimethyl Sulfoxide-Triphosgene Manganese Dioxide Pyridinium Chlorochromate Pyridinium Dichromate Ruthenium(rV) Oxide Silver(I) Carbonate on Celite 1,1,1-Triacetoxy-1,1-dihydro-1,2-benziodoxol-3( 1 H)-ons. 

Alcohol (mmol) Triphosgene (mmol) Pyridine (mmol) rieldof hydantoins 26(%)... 

A series of non-commerdally available chloroformates (R OCOCl) 25 (Table 4.2) were claimed to be synthesized from the desired alcohol and triphosgene in the presence of pyridine [24]. 

Chloroformates 34 of some levorotatory 8-substituted menthols 33 have been prepared with triphosgene in the presence of pyridine [28]. 

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