Oxime orthoesters

An additional type of orthoester was reported by Kunz [513]. Specifically, the oximate orthoester 233 reacted in BF3-Et20-promoted reactions to give fm/i5 -glycosides. 

Kunz, H, Pfrengle, W, Effective 1,2-tranr-glycosylation of complex alcohols and phenols using the oximate orthoester of 0-pivaloyl glucopyranose, J. Chem. Soc. Chem. Commun., 713-714, 1986. 

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

Open-chain alkanes, alkyl halide reduction, 29-31 Organosilicon hydrides bond strengths, 5-6 hypervalent silicon species, 9-11 ionic hydrogenation, 5 trivalent silicon species, 7-9 Orthoesters, reduction of, 97-99 Oxime reduction, 102... 

Oximes can be also used for the imidazole ring synthesis. Thus, reaction of a-amino-oximes 122 and orthoesters leads to imidazole Af-oxides 123 (equation 53) . Interaction of a-ketooxime 124 with triazinanes also afforded imidazole Af-oxides 125 in good yields (equation 54) . Similarly, a-ketooximes in the system NH3/H20/aromatic aldehyde afforded trisubstituted 1-hydroxyimidazoles . ... 

The cyclization of a-hydrazono oximes (635) with orthocarboxylates is an excellent way of preparing 1,2,4-triazine 4-oxides (636) (73TL1429,7lLA(750)12,77LA1713). Using aldehydes or ketones instead of orthoesters provides 2,3-dihydro derivatives (637 Scheme 22) (75S794). Cyclization of a-hydrazonocarboxamides (638) with carbonic acid derivatives such as ethyl chloroformate affords l,2,4-triazine-3,5-diones (639) (68M1808). The a-hydrazonocarboxamides (638) can be prepared by the reaction of diazonium salts with a-activated acetamides such as cyanoacetamide as shown. 

A procedure for l-alkyl(aryl)-177-4-methylimidazole Af-3-oxides 1539 involves the cyclocondensation of a-amino-oximes, for example, 1537, and orthoesters 1538. Low yields (6-27%) in the cyclization process are due to the predominant Z-stereoisomer around the oxime moiety in 1537 (Scheme 397) <2004S2678>. 

Nitrosolysis of camphor ethyl acetal with ethanolic ethyl nitrite in sulphur dioxide yields the orthoester oxime (205) which is rapidly dehydrated by excess acetal to the orthoester nitrile which then reacts with sulphur dioxide to form the ester nitrile and diethyl sulphite.Further papers in this section include the full paper on ozonolysis of silyl ethers (Vol. 5, p. 33), another synthesis of camphor-enol trimethylsilyl ether (cf. Vol. 6, p. 41)/°° the conversion of camphor oxime with Grignard reagents into the corresponding imine with no aziridine formation/° the preparation of (206) by treating bornylene with trichloroacetyl isocyanate/ the oxidation of thiocam-phor to the 5-oxide and alkylation in the presence of thallium(i) ethoxide to a/S-unsaturated sulphoxides/ and the free-radical C-3 alkylation of camphor with alkenes. " ... 

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