Imino group, determination

In contrast to ketenes, keteneimines readily undergo metal-catalyzed [3+21-cycloadditions with methylenecyclopropanes. Depending on the substituents in both educts, pyrroles, a-methylene-A3-pyrrolines or iminocyclopentenes can be synthesized selectively in good to excellent yields. The substituent of the imino group determines... 

Spindler and Frechet used 3,5-bis((benzoxy-carbonyl)imino)benzyl alcohol which decomposed thermally in THF solution containing DBTDL as a catalyst [97]. The resulting polymer was found to be insoluble unless an end-capping alcohol was added from the beginning. The end-capping groups determined the properties of the polymers such as glass transition temperature, thermal stability, and solubility. 

The previously unknown l,2,4-thiadiazole 4 oxides 64 were prepared by condensation of benzamidoximes or their derivatives with Appel salt (Scheme 4) <1996CC1273>. The reaction mechanism includes attack of the imino group in 65 on the S-l atom of the 1,2,3-clithiazole ring. The /V-oxidcs are shown to be the 4-isomers by analysis of the NMR and mass spectra of lsN-labeled and unlabeled products and X-ray structure determination of the derived carboxamide 66 <1999J(P1)2243>. 

The first step in the ring closure of carboxamide 107 (R=NH2) with imidates is the formation of an amidine intermediate, with subsequent nucleophilic attack of the imino group of the amidine on the carbonyl group this takes places with loss of the carboxamide iV-substituent [117]. This observation formed the basis of a simple synthesis of CHINOIN 143 enantiomers. From carboxamides 39 and 40 with ethyl m-chlorobenzimidate, 109 and 110 were obtained in high enantiomeric purity. The absolute configurations were determined by hydrolysis of 109 and 110 to the corresponding amino acid, which was identified by HPLC [79]. 

Certain derivatives of benzamide tend to confirm this view. When the silver salt of benzamide is treated with ethyl iodide, the metal is replaced by the alkyl radical. The product formed is determined by the temperature at which reaction takes place. The substance obtained at room-temperature yields ammonia and has the formula given below. It belongs to the class of compounds known as iminoesters, which may be considered as derived from esters by the replacement of the oxygen atom of the carbonyl group by the bivalent imino group, =NH. Like esters it yields an alcohol on hydrolysis at the same time the imino group is replaced by oxygen. 

The stereochemistry of the macro cyclic moiety in pinnatoxins B (2) and C (3) was determined as follows. Reduction of the imino group in 2 and 3 with NaBH4 followed by oxidative cleavage with NaI04 provided aldehyde 6 (Scheme 1). Aldehyde 6 was also obtained by the reduction of iminium and a carboxylic acid moiety in pinnatoxin A methyl ester (5) followed by oxidation of the resulting alcohol. Since the spectroscopic data of 6 derived from 2 and 3 and that from 5 were identical, the relative stereochemistry of the macrocyclic core in 2 and 3 was confirmed to be the same as that in piima-toxin A (1). 

The absolute sense of twist between the two amino groups of the diaminocyclohexane of kasugamin 85 can be determined from the signs of exciton-split c.d. corves of derivatives 86 bearing two chromophoric imino groups. The protonated forms lead to strong bathochromic and hypochromic shifts. Similar derivatizations were applied to methyl a-L-acosaminide and daunosamine. The effects of stereochemistry and solvent on o.r.d., c.d. and u.v. spectra of 1-nitrophenyl D-galactopyranosides has been described. 

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