C-Formylation

Pyrazole, C-formyl-conformation, 5, 209 Pyrazole, fluoro-reactions, 5, 263, 267 Pyrazole, 4-fluoro-5-hydroxy-tautomerism, 5, 214 Pyrazole, 1-germyl-synthesis, 5, 236 Pyrazole, halo-halogenation by, 5, 54 reactions, 5, 104, 105, 266 reduction, S, 105, 106, 266 Pyrazole, 3-halo-1-phenyl-quaternary salts... 

In the Meth-Cohn quinoline synthesis, the acetanilide becomes a nucleophile and provides the framework of the quinoline (nitrogen and the 2,3-carbons) and the 4-carbon is derived from the Vilsmeier reagent. The reaction mechanism involves the initial conversion of an acylanilide 1 into an a-iminochloride 11 by the action of POCI3. The a-chloroenamine tautomer 12 is subsequently C-formylated by the Vilsmeier reagent 13 derived from POCI3 and DMF. In examples where acetanilides 1 (r = H) are employed, a second C-formylation of 14 occurs to afford 15 subsequent cyclisation and... 

Chemical Name 0-2-deoxy-2-(methylamino)-o -L-glucopyranosyl-(1->2)-0-5-deoxy-3-C-formyl-a-L-lyxofuranosyl-(1->4)-N,N -bis(aminoiminomethyl)-D-streptamine... 

Dimethyl-2(l//)-quinoxalinethione gave 3-(2-dimethylamino-1 -formylvinyl)-1 -methyl-2(l//)-quinoxalinethione (86) Me2NCHO, POCI3, 0°C 20 min then substrate, 60°C, 5h 78% note the additional C-formylation)." " ... 

Note Although rare, passenger introduction of extranuclear C-formyl groups into quinoxaline is possible as exemplified here. 3-Methyl-2(177)-quinoxalinone (174) with terephthalaldehyde gave 3-p-formyl-... 

These reactions are most important for the preparation of acyl fluorides. " Acyl chlorides and anhydrides can be converted to acyl fluorides by treatment with polyhydrogen fluoride-pyridine solution" or with liquid HF at — 10°C. Formyl fluoride, which is a stable compound, was prepared by the latter procedure from the mixed anhydride of formic and acetic acids. Acyl fluorides can also be obtained by reaction of acyl chlorides with KF in acetic acid or with DAST. Carboxylic esters and anhydrides can be converted to acyl halides other than fluorides by the inorganic acid halides mentioned in 10-77, as well as with PhsPXa (X = Cl or but this is seldom done. Halide exchange can be carried out in a... 

Note Although rare, passenger introduction of extranuclear C-formyl groups into quinoxaline is possible as exemplified here. 

Ci2H20O4S2 5-Deoxy-3-C-formyl-1,2-O-isopropylidene- -L-lyxofuranose 31-(trimethylene dithioacetal) DFPLXT10 34 32 358 366... 

A particularly interesting reaction is the C-formylation[2] of alkylidenephosphoranes by A-formylimidazole to give a-formyl derivatives (C6H5)3P=C(R)CHO which can be further transformed into a,/ -unsaturated aldehydes by Wittig reaction, or hydrolyzed to produce aldehydes RCH2-CHO. 

One of the more difficult problems encountered in obtaining a valid assay of formic acid is that of formate ester formation. The formate is derived from the cyclic, hemi-acetal structure which is an equilibrium form of many free sugars in solution. For example, the oxidation of one of the cyclic forms of D-glucose can readily be seen to give a formate ester (as well as a C-formyl group) on the atom originally denoted as C5. It... 

Streptose is the first branched-chain sugar to have been identified as a component of a biological compound produced by a microorganism. This dicarbonyl sugar is known only in its derivatives. The chemistry of streptose and streptomycin has been lucidly reviewed by Lemieux and Wolfrom.1 In this article, it was noted that streptose must be either 5-deoxy-3-C -formyl-L-ribose or 5-deoxy-3-C-formyl-L-lyxose. Since then, the presence of the latter configuration (XXXIV) has been definitely established by Wolfrom and DeWalt,66 who found that N-acetyltetrahydrostreptobi-... 

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