Imino derivatives, of metals and

The direct monoalkylation of a steroidal 4-en 3-one at C-4 calls for delicate control of reaction conditions and at best gives products containing some 4,4-dialkylated material. Indirect procedures for monomethylation (e.g. 4-thio-methylation-desulphurization ) are now supplemented by a novel method using the 3-imino-derivatives (315). Metallation (e.g. with lithium di-isopropyl-amide) gives the salt (316). which is selectively mono-alkylated at C-4, giving the 4-alkyl-4-en-3-one (317) after hydrolysis. 

Reactions of metallated hetarenes with carbonyl compounds and their imino derivatives 99PHC21. 

Pyridine derivatives with additional donor functions and sterically demanding substituents have been used with the intention of producing complexes of Cd (and of other metals) with low coordination number one of these ligands is the tridentate, planar-bonding 2,6-bis[(2,6-dimethyl-phenylimino)methyl] pyridine (pydim a Schiff base derived from 2,6-pyridine dialdehyde), which with Cd(BF4)2 and thiocyanate gives a dinuclear complex [(pydim)Cd(/x-NCS-S,N)]2(BF4)2 with N-dominated coordination sphere.191 As centrosymmetric Plijc, Z= 2), the complex has an antiparallel /x-1,3 NCS double bridge with Cd—N and Cd—S bonds (224.6 pm and 255.5 pm, respectively) the Cd—N(py) bond is clearly shorter than the Cd—N(imino) bonds (225.6 pm and 245.0 pm,... 

A group at the Academy of Sciences in Moscow 197) has synthesized chiral threonine. Derivatives of cyclic imino acids form copper complexes with glacine and carbonyl compounds. Hydroxyethylation with acetaldehyde and decomposition of the resulting complexes produced threonine with an optical purity of up to 97-100% and with threo/allo ratios of up to 19 1 197). The chiral reagents could be recovered and re-used without loss of stereoselectivity. The mechanism of this asymmetric synthesis of amino acids via glacine Schiff base/metal complexes was also discussed 197). 

Allylation of carbonyl and imino groups is one of the most convenient methods for the introduction of allylic functions.107-110 Allylic tin compounds have high interaction between C=C and C-Sn bonds which makes them more reactive than the corresponding silicon derivatives.111,112 In spite of their high reactivity, tin compounds are stable enough to be isolated and to react at ambient temperature under aerobic conditions. These factors allow them to be applicable to various types of reactions, for example, thermal,113 high-pressure,116 transition metal-catalyzed,117,118 radical,119,120 photochemical,121,122 tin-lithium exchange reactions,108,113 and so on. A broad... 

This procedure, a variant of method 3, is also potentially a very useful method. An advantage is that the pH of the reaction mixture is controlled by the amount of amine present. In theory, the use of this method would permit the preparation of metal derivatives of a wide variety of /8-keto imines and obviate the need for preparation and isolation of the individual ligands. In practice, it appears that of the possible compounds the most stable metal chelate compound is formed. This may not always be the desired compound. Thus, even in the presence of copper-(II) ion, the condensation of 4-imino-2-pentanone and trimethylenediamine was not successful, the product isolated being bis(4-imino-2-pentanonato)copper(II). ... 

This volume of Inorganic Syntheses contains sixty-eight contributions. Two articles of a review nature are included, one on metal derivatives of jS-keto imines (jS-imino ketones) and the other on the chemistry of the noble gases. 

More recently the introduction of low-valent transition metal and lanthanoid based reducing systems, especially those based on titanium, has provided dramatic advances in efficiency and selectivity. It is now possible to select appropriate conditions for efficient coupling of all types of carbonyl compounds, often with high chemo-, regio- and stereo-selectivity. Moreover, imino- and thio-carbonyl derivatives are also coupled via pinacolic methodology. The coupling of imines to 1,2-diamines is particularly effective, with excellent control of vicinal stereochemistry. 

Tautomerism of 2-Aminothiazoles. - The imino-form (101) predominates only when the S02Ar group is bonded to the exocyclic nitrogen atom In all other cases the amino-form (102) is prevalent. The and Hn.m,r., i.r., and u.v. spectra of 4- or 5-substituted 4-thiazolin-2-ones and their N-or 0-Me derivatives were studied. The i.r. and n.m.r. spectra show that the parent compounds exist entirely or predominantly in the 2-oxo-form in solution. In contrast, u.v. and n.m.r. spectroscopy did not clearly distinguish between the 2-oxo- and 2-hydroxy-stnictures. The kinetics and mechanism of spontaneous acid-, base-, and metal-ion-induced hydrolyses of A salicylidene-2-aminothiazole were also described. Studies on the polymorphism of sulphathiazole and its crystallographic behaviour under pressure have also been reported. ... 

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. 

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