Oxime carbonates

Carbon chemical shifts were employed in studies of conformational effects on aldoximes and ketoximes. They appear in the region 145 to 163 ppm and several values are illustrated in Table 2. Such resonances are some 50 ppm to higher field relative to the corresponding carbonyl resonance. Where substimtion is asymmetrical, differences in oxime carbon chemical shifts are observed, depending upon the conformation of the oxime N—OH. Such conformational isomerism also has a profound effect upon the chemical shift of the a-carbon. 

TABLE 2. Carbon-13 chemical shifts of oxime carbons ... 

Phenoc-protected amines were prepared in two ways. The first involved the reaction of an amino acid with the oxime carbonate 5 to yield 6 as shown in Scheme 7. The second method consisted of reaction of the a-hydroxy ketone with an isocyanate. Preparation of the phenacyl chloroformate was attempted, resulting in a cyclic carbonate which was inert to amines. 

Although imidoyl iodides are chemically labile, their in situ generation from oxime derivatives with trimethylsilyl iodide or diethylaluminum iodide has been ascertained spectroscopically (equation 14). The synthetic utility of these reactive species has been demonstrated by further reacting them with external nucleophiles such as thiolates or Grignard reagents. For example, the imidoyl iodide (28), generated from acetophenone oxime carbonate with trimethylsilyl iodide, is further transformed to ethylthioimidate (29) and a-alkylated amine (30), respectively (Scheme 1 and equation 15). 

Oximes that have quaternary carbons adjacent to the oxime carbon are prone to undergo fragmentation as a major reaction pathway, furnishing nitriles. Steroidal ketoxime (50) and tetrahydrofuranyl ketoxime (52) give nitriles (51) and (53), respectively, as major products (equations 36 and 37). 4s... 

In general, oximes react as though they were primary alcohols. Thus, treatment of RR C=NOH (R = CN, R = Ph, 4-ClCjH or 1-naphthyl R = COjEt or CHjCjO), R = COjEt R = R = Ph) with COCl in inert solvents and in the presence of base results in the formation of RR C=NOCOCl, which was then treated in situ with MCgCOH to give the corresponding oxime carbonate [1014]. 

Ketones Aldehydes Quinones Carboxylic acids and derivatives Thioureas Ureas Oximes Carbonates Imines Isocyanides Cyanides Isothiocyanates Thiocyanates Isocyanates Cyanates Carbodiimides Heteroaromatics Aromatics... 

Use of the oxime of D-camphor in the catalytic hydrosilylation leads to the formation of only 5 % of endo- and 13 % of e.YO-bornylamine. A further product is obtained in 79 % yield, the formation of which requires the hydrogenolytic cleavage of the five-membered ring in the camphor skeleton between the bridgehead carbon atom and the oxime carbon atom. The product, (+ )-(l/ ,3A)-l -(2-aminoethyl)-2,2,3-trimethylcyclopentane, was shown to be enantiomerically pure88. 

O-Allyl oxime carbonates -, C-allylation with - 43, 723 Allyloxy-2-acetylenes... 

Oxamic acid esters Oxime carbonates Oxime orthoesters a-Peroxyoximes... 

Oxime carbonates of type R2C=N—O—CO—O—allyl have been mentioned in the context of this paragraph. " ... 

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

Isocyanatoformic acid esters 2-NitroenoIethers Oxime carbonates... 

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