Chlorocarbonyl ketenes

C14H20CINO2) see Bietamiverine phenyl(chlorocarbonyl)ketene (QHjCIOj 17118-70-6) see Carindacillin phenyl chloroformate... 

A one-pot synthesis of pyrano[3,2-c]quinolin-2,5(<5/7)-dione 107 was reported through the condensation reaction of chlorocarbonyl ketenes 108 with 4-hydroxyquinolin-2(l//)-ones 109. This simple procedure was shown to be a convenient synthesis of pharmacologically active compounds in high yields <06S435>. 

It is well known that l,3-thiazine-4,6-diones can exist in three tautomeric forms <1960CB671, 1976KGS1042>. Cycloaddition of chlorocarbonyl ketenes with thioamides has been reported to produce only the 4-hydroxy-l,3-thiazin-6-ones, whereas the same reaction with amides gives either 4-hydroxy-1,3-oxazin-6-ones or a mixture of tautomers depending on the substituents on the starting materials <2005ARK(xv)88>. 

Chlorocarbonyl ketenes 126 have been found to act as highly effective... 

Reaction of chlorocarbonyl ketenes 126 with N-substituted cinnamic amides, resulted in mesoionic 1,3-oxazinium 4-olates 341 which can be subjected to ring-opening to afford ketenes 342 which in turn is submitted to an intramolecular criss-cross [2 - - 2] cycloaddition reaction via TS to give 3-aza-bicyclo[3.1.1]heptanetriones 343 in reasonable yields (Scheme 106) (2005JOC5859). 

The products, obtained from the cycloaddition of chlorocarbonyl ketenes 126 with N-unsubstituted a, 8-unsaturated amides or aromatic amides are quite different from the those obtained from the cycloaddition of... 

Phenyl(chlorocarbonyl)ketene 170 reacts with N-phenylacetyknorpho-line forming 4-hydroxy-6-morpholino-3,5-diphenylpyran-2-one in a process interpreted as involving initial esterification of the acylketene with the enol of the amide followed by generation of a second acyl ketene 171 and further cyclization to 172 (Eqn (4.109)). Ketene 170 also reacts similarly with 1,3-diketones and heterocyclic 3-hydroxy-2-ene-l-ones forming polycyclic lactones. 

Bielectrophiles have found appreciable applications in the synthesis of ring-fused systems, especially those involving [5,6] fused systems. The following serve to illustrate these applications. Reaction of pyrazole with (chlorocarbonyl)phenyl ketene (214) (Type 1, Scheme 6) readily formed the zwitterionic pyrazolo[l,2-a]pyrazole derivative (215) (80JA3971). With l-methylimidazole-2-thione (216), anhydro-2-hydroxy-8-methyl-4-oxo-3-phenyl-4//-imidazo[2,l-6][l,3]thiazinium hydroxide (217) was obtained (80JOC2474). 

Oxazin-4-ones are obtained by cycloadditions between isocyanates and ketenes (Scheme 37). Routes to 1,3-oxazinium salts consist of 1,4-cycloadditions either between a,(3-unsaturated (3-chlorocarbonyl compounds and nitriles or between /V-acylimidoyl chlorides and alkynes. Tin(IV) chloride is an effective catalyst for both reactions (c/. Scheme 38). 

Diketones and a-(chlorocarbonyl)phenyl ketene react to provide the intermediate ketene 645, which can cyclize to afford 2/7-pyran-2-ones in high yield (Scheme 150) <2004T5931>. Similarly, silyl enol ethers react with ot-(chlorocarbonyl)mesitylketene to afford 2//-pyran-2-ones (Equation 260) <2001T4133>. 

Reaction of 1,2-allenyl esters and 1, catalyzed by potassium carbonate, gave 456a through a tandem nucleophilic addition-lactoniza-tion process (06S2731). The (chlorocarbonyl)phenyl ketene was condensed with 1 to give 456 (R = Ph) (04T5931). 

The addition of (chlorocarbonyl)phenyl ketene 126 to 3-alkyl-1-phenyl-2-pyrazolin-5-ones 141 resulted in 4-hydroxy-3-alkyl-l,... 

A sulfur analogue of pentamethylene ketene 220 has been synthesized via the dehydrochloiination of 2-chlorocarbonyl-l,3-dithiane 219. Numerous spiro l,3-dithiane-2,3 -(5 6 -polymethylene) dihydropyranones 221 were synthesized via the in situ interaction of 2-carbonyl-l,3-dithiane 219 with the 2-(aminomethylene)cycloalkanones 101 (Scheme 69) (1976JHC1105). 

The condensation of (chlorocarbonyl)phenylketene or (chlorocarbonyl) benzylketene with 1,3-dinucleophiles such as N-phenylthiocarbamates 520a and N-phenylcarbamates 520b resulted in the generation of relatively unstable mesoionic 1,3-thiazinium 4-olates I or 1,3-oxazinium 4-olates II which can be transformed into 3,5-diaryl l,3-thiazine-2,4,6-triones 521 and alkoxy-3,5-diphenyl-3H-l,3-oxazine-2,6-diones 522 (Scheme 172). In accordance with proposed mechanism, the nitrogen atom of 520 attacks the central carbon atom of the ketene group, with a low-lying LUMO,... 

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