1.1- Enediamines synthesis

Carbodiimides serve well in the 1,1-enediamine synthesis due to the 1,3-diazo arrangement in its structure. An earlier report on the preparation of 1,1-enediamines from carbodiimides appeared in 1965 by Gompper and Kunz98. In the presence of base, carbon acids add to carbodiimides 79 to give enediamines 80 in moderate to excellent yields (equation 26)98,99. Due to the structural feature of carbodiimides, only acyclic 1,1-enediamines can be expected. However, cyclic structures at the jS-carbon atom (80a) were also obtained. 

The most widely applied precursors for the synthesis of monocyclic NHPs are a-diimines which can be converted to the target heterocycles either in a two-step reaction sequence involving two-electron reduction of the diimine to an enediamide, enediamine, or a-aminoamine and subsequent condensation with PC13 [18-20] or a dichlorophosphine RPC12 [21], or via direct base-promoted reaction with PC13 [20, 22], The latter reaction involves addition of a P-Cl bond to each imine moiety followed by base-promoted elimination of hydrogen chloride leading to 2,4-dichloro-... 

The two-electron reduction of a-diimines to prepare the required starting materials for a subsequent condensation is usually achieved by reaction with lithium but other alkaline (Na) or alkaline earth (Mg) metals should be useful as well. The synthesis of the heterocycles 10 is either accomplished by direct metathesis of the formed metal enediamide with PC132 [19] or, alternatively, by quenching the diamide with a suitable acid to produce an enediamine or a-aminoimine, respectively, and subsequent base-induced condensation with PC13 or RPC12 [18, 20] (Scheme 3). 1,3-l )i-/e/t-butyl-2-chloro-1,3,2-diazaphospholene was also prepared from the reaction... 

The chemistry of coordination compounds comprises an area of chemistry that spans the entire spectrum from theoretical work on bonding to the synthesis of organometallic compounds. The essential feature of coordination compounds is that they involve coordinate bonds between Lewis acids and bases. Metal atoms or ions function as the Lewis acids, and the range of Lewis bases (electron pair donors) can include almost any species that has one or more unshared pairs of electrons. Electron pair donors include neutral molecules such as H20, NH3, CO, phosphines, pyridine, N2, 02, H2, and ethyl-enediamine, (H2NCH2CH2NH2). Most anions, such as OH-, Cl-, C2042-, and 11, contain unshared pairs of electrons that can be donated to Lewis acids to form coordinate bonds. The scope of coordination chemistry is indeed very broad and interdisciplinary. 

In contrast to enamines1,2, the chemistry of 1,1-enediamines have been only briefly studied although the earliest reports3,4 of such compounds may date back to the 1940s. This has been partly due to the relative difficulty of the synthesis of simple 1,1-enediamines 1 in earlier years. A convenient method for the preparation of conjugated... 

The method has been extended to the synthesis of cyclic 1,1-enediamines with nitro and other electron-withdrawing substituents on the /f-carbon atom39,96. For example, l-methyl-2-methylthio-4,5-dihydroimidazoline (74) reacts with nitromethane, and diethyl malonate, malononitrile and alkyl cyanoacetates at 100 °C to yield products 75 in 56-78% yield (equation 25)39. 

In an attempted synthesis of the spiro compounds 123 from the cyclic 1,1-enediamines 122 derived from cyclic ketones, in contrast to the expectation, the cyclic ketone ring is cleaved under mild reaction conditions and fused heterocyclic compounds 124 are obtained in good yields from 122 and ethyl propiolate (equation 43)58,122. 

Tris(2,4-pentanedionato)molybdenum(III), synthesis 39 Potassium tetraoxalatouranate(IV), synthesis 40 Trifluoromethyl hypofluorite, synthesis 42 Bis(ethylenediamine)dioxorhenium(V) chloride, bis(ethylene-diamine)oxohydroxorhenium(V) perchlorate, and bis(ethyl-enediamine)dihydroxorhenium(V) hexachloroplatinate(IV), synthesis 44... 

Synthesis of a tetracyclic analog of 294 is also reported from the anhydride of pyrazine-2,3-dicarboxylic acid and a tetralin derivative under Friedel-Crafts conditions (85JCR(S)338). A representative of the o-quinonoid system (296) was prepared from 2,3-dichloro-1,4-naphthoquinone and o-phenyl-enediamine (63JOC1019). 

A related synthesis of fused pyrazines employs 3,4-dlamlnothlophenes (ingeniously prepared from pyridine as depicted below) as latent enediamines condensation with 1,2-dicarbonyl compounds gives thieno(3,4-b)pyrazines which would appear to potential intermediates to novel pyrazines by reductive desulfurization. 

The resolution of tetramisole into levamisole, L-(-) [a]p = -54.7 (H2O), and D-(+) [a]p = + 83.0 (H2O) enantiomers has been achieved using d-lO-camphorsul-phonic acid [4]. The absolute configuration of the isomers was established by carrying out their stereospecific synthesis starting from D(+) and L(-)-l-phenylethyl-enediamines (32) as shown in scheme 6 [5]. 

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