Iminoester

Photolysis of 3-methyl-1,2-benzisoxazole in n-hexane/acetonitrile produced a salicyl-amide. In contrast, photolysis in acetonitrile/methanol (95 5) gave an iminoester which subsequently hydrolyzed to methyl salicylate (Scheme 11) (74HCA376). 

The mechanism of thermolysis and photolysis of ethers of 3-hydroxy-1,2-benzisoxazole has also been studied. Heating of the allyl ether (43) gave minor amounts of (44) and two benzoxazoles. Photolysis of (45) in methanol gave a benzisoxazole and an iminoester, via intermediate (46). Thermolysis at 600 °C gave a benzoxazole, a benzoxazolone and cyano-phenol (Scheme 16) (71DIS(D)4483). 

The reaction of aliphatic primary amines with alkyl a-hydrogenoperfluorocar-boxylates leads to the corresponding P-alkyl iminoesters as the major or the sole tautomers, depending on the length of the perfluoroalkyl chain [ 103] (equation 89). 

Surprisingly, arylhydrazones 88a-d, upon treatment with 1-benzenesulfonyl-hydrazide 89 in refluxing ethanol, afforded very good yields of pyrazol-3-ones 90a-d (85JIC54) (Scheme 25). 5-Aminopyrazol-3-(Mies have also been synthesized from /3-cyanoesters (Section II,A,2) and from /3-iminoesters (Section II,A,3). 

A more useful method for the synthesis of 1,2,4-tiiazine 4-oxides is the cyclization of a-hydrazonooximes 141 with orthocarboxylates or iminoesters. A variety of 1,2,4-triazine 4-oxides 55 were obtained by this methodology (71 LA 12, 73TL1429, 77LA1713, 78JMC623, 86JHC721, 87KGS257). 

Nitriles react with alcohols in the presence of hydrochloric acid to form iminoester hydrochlorides, which are hydrolyzed to the esters (Pinner synthesis). Heitz and coworkers [21-23] published several fine papers on the polyazoester synthesis from the reaction of a series of poly(oxyethylene) glycol or poly(oxypropylene) glycol and AIBN in the presence of dry hydrochloric acid at 0-5°C according to Pinner synthesis. Condensation reactions of ACPC and dihydroxy terminated poly(oxy-ethylene) glycol yield polyazoesters [24,25]. 

Aliphatic dinitriles, such as adipodinitrile, react with aliphatic diols at low temperature (0-5°C) in the presence of HC1 and form poly(iminoesters) which... 

Scheme 16 Diastereoselective synthesis of 2,3-diamino esters and alcohols by the addition of achiral glycine iminoester enolates to chiral M-sulfinylimines...

Scheme 18 Reagent-induced enantioselective catalytic synthesis of 2,3-diamino esters by addition of a-amino and a-iminoester enolates to imines...

Imidates 60 were prepared in two steps by first reacting nitrile derivatives with various alcohols. The condensation of the obtained iminoester with appropriate acetyl chloride resulted in the formation of the title compounds 60a-c (Scheme 12). The structures of the products 60 were elucidated by means of spectroscopic analysis. 

Nitrous acid or alkyl nitrites react with a number of nitrogen compounds to yield tetrazoles. For example, hydrazidines (87), which can be prepared in situ from the corresponding iminoesters, react with nitrous acid or its derivatives to give 1-substituted tetrazoles (88).150-152 This reaction (Eq. 17), is one of the most extensively used methods for the synthesis of... 

Thermal reactions of N-aryl cyclopropenone imines 268 are differentiated by the nature of the N-aryl substituent. Imines 268 (Ar = phenyl, p-nitro-phenyl) undergo isomerization to N-aryl-2-phenyl-indenone imines 271 when heated in aprotic solvents202. Since in protic solvents, e.g. ethanol, only the iminoester 272 is isolated, evidence seems to be given for the intermediacy of 269 implying carbene and ketene imine functionality, which may either cause electrophilic ring closure with a phenyl group to form 271 or may add to the hydroxylic solvent (272). 

Reactions of 4-aminofurazan-3-carboxylic acid iminoester 122 with o-aminophenol, phenylenediamine, ethylene-diamine, and aminoethanol give compounds 123-126 (Scheme 33) <2002RJ0872>. 

Reaction of the germene 14 with LiF in the presence of iminoesters or iminophosphonates (Equation (18)) leads to 3-germapyrrolidines.29... 

This particular function, and also others of the metal, are also beautifully utilized in the work on the chemical synthesis of corrins (Fig. 6.2). In the synthesis of 2, a metal, Co(ll), Ni(ll) or Pd(ll), is required to stabilize the precursor 1, which would otherwise be extremely labile configurationally and constitutionally. As added bonuses, the metal ion helps to activate the methylene carbon for its attack on the iminoester carbon, and also forces the four nitrogens into a planar conformation, thereby bringing the condensation centers of rings A and B close together. This is strikingly shown by X-ray structural determination of 1. With... 

Pentamidine Pentamidine, 4-4 -(pentamethylendioxy)dibenzamidine (37.4.2), is made by reacting 4-hydroxybenzonitrile with 1,5-dibromopentane in the presence of sodium hydroxide to make l,5-few-(4-cyanophenoxy)pentane (37.4.1). Subsequent reaction of this with an ethanol solution of hydrogen chloride with the intermediate formation of an iminoester, and then with an ethanol solntion of ammonia gives the desired pentamidine [55-57]. 

Pyrantel Pyrantel, l,4,5,6-tetrahydro-l-methyl-2-[trans-2-(2-thienyl)vinyl]-pyrimidine (38.1.22), a derivative of tetrahydropyrimidine, is made from 3-(2-thienyl)-acrylonitrile (38.1.19), which is made in a Knoevangel condensation of fnrfnral with cyanoacetic acid. Acidic hydrolysis of this makes 3-2(-thienyl)acrylamide (38.1.20). Reacting this with propansnUone gives an iminoester (38.1.21), which when reacted with A-methyltrimethyl-enediamine gives the desired pyrantel [20-23]. 

SCHIiME 94. Addition of a tertiary alkylzinc reagent to a chiral iminoester... 

In a related reaction a-amino ketones (175) with iminoesters RC(NH)OMe give imidazoles (175 — 176). 

The pyrrolo[2,3-c]pyridine (53) reacts with O-mesitylhydroxylamine, followed by ethyl chloroformate/potassium carbonate, to give the N-iminoester (54). Irradiation of (54) gives a mixture of three rearranged products and starting material (53 Scheme 17) (81CPB1539). 

The addition of HC1 to a mixture of an alcohol and a nitrile in the absence of water leads to the hydrochloride salt of the iminoester (27) (Reaction XXI). 

The electroreductive cyclization of chiral aromatic a-iminoesters 175, prepared from ( )-a-amino acids such as (6)-valine, (A)-leucine, and ( -phenylalanine, in the presence of chlorotrimethylsilane and triethylamine afforded mixed ketals of ar-2,4-disubstituted azetidin-3-ones 176 stereospecifically (>99% de and 85-99% ee) (Equation 46) <2003JA11591>. The best result was obtained using tetrabutylammonium chlorate as a supporting electrolyte and a platinum cathode. 

The intramolecular cyclization of /3-carboethoxy-/ -amino acid 379, synthesized from L-proline-catalyzed Mannich reaction of aldehydes with an iminoester and subsequent oxidation, with sodium hydroxide yielded the cyclopentane-spirofused azetidin-2-one 380 (Scheme 56) <20040L2507>. 

An enantioselective version of this reaction has been reported by Rueping et al.102 Treatment of an a-iminoester and an alkyne with silver acetate and a binol phosphate derivative gave propargylic amines with the highest enantiomeric ratio (er) reported as 96 4. Although the proposed catalytic cycle invoked the in situ formation of the... 

TABLE 2.1. Effects of Acid on the Cycloaddition of Iminoester (21) and Methyl Propiolate (22)... 

Scheme 2.8 Optimization of the dipolar cycloaddition of iminoesters. See Table 2.2 for details.

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