Formamidines structures

These thiazoles are of specific interest in that they display exceptional pharmacological properties. Additionally, the unsaturated 2-aminonitrile functionality of the above thiazoles is recognized for its versatile functionality and therefore for its ensuing significance in the synthesis of heterocycles. The synthetic utility of thiazoles 13a-f is illustrated by the reactions of the unsaturated 2-aminonitrile functionality in compounds 13b and 13c with formamidine acetate, resulting in the thiazolopyrimidines 14a and 14c respectively. The synthesis of this relatively rare family of heterocycles provides a route into structurally similar bioactive compounds. ... 

In the presence of N,N,N, N",N"-pentamethyldiethylenetriamine ( = PMDETA), monomeric lithium complexes of bulky formamidinate ligands can be isolated. The compounds (Scheme 12) comprise a Li(PMDETA) center coordinated by a bulky formamidinate in either the E-syn- or E-anti-isomeric form. Two of the structures display coordination of the pendant amidinate imine, and can therefore be considered the first examples of if. r -C = N,N metal amidinate coordination. ... 

ET-IR spectroscopy was employed to investigate the structures of the 1 1 complexes between Li" and the guanidine-substituted azo compounds pyiidine-2-azo-p-phenyltetramethylguanidine and 4,4 -bis(tetramethylguanidine)azoben-zene. Both Li" complexes exist as dimers in acetonitrile solution.The structural chemistry of potassium N,N -di(tolyl)formamidinate complexes has been investigated in detail. These compounds were prepared by deprotonation of the parent Af,N -di(tolyl)formamidines with potassium hydride (Scheme 13). The resulting adducts with either THE or DME display one-dimensional polymeric solid-state structures that exhibit /r-fj fj -coordinated formamidinates. 

The structural investigations have been extended to potassium derivatives of the "super" formamidine HC(NC6H3Pr2-2,6)(NHC6H3Pr2-2,6) ( = HDippForm). Treatment of the free formamidine with KN(SiMe3)2 yielded the formamidinate species [K(DippForm)2K(THF)2l (THF) , which exhibits a macromolecular structure of alternating fj -arene f/ -amidinate bound potassium di-amidinate and potassium di-THF units in a one-dimensional polymeric array (Figure 5). Addition of a further equivalent of HDippForm afforded hydrogen-bonded [K(DippForm)(THF)3](HDippForm). ... 

Structural studies have also been carried out on related alkali metal complexes of N,N -di(o-fluorophenyl)formamidine (= HFPhF). Preparations... 

In closely related studies, the molecular and crystal structures of lithium, sodium and potassium N,N -di(p-tolyl)formamidinate and N,N -di(2,6-dialkyl-phenyl)formamidinate complexes have been elucidated. These showed the anions to be versatile ligands for alkali metals, exhibiting a wide variety of binding modes. ... 

The role of steric influences on the formation of various vanadium amidinate complexes in the oxidation states +2 and +3 has been studied in detail. The reaction of VCl2(TMEDA)2 and of VCl3(THF)3 with 2 equivalents of formamidinate salts afforded dimeric V2[HC(NCy)2l4 (cf. Section IV.E) with a very short V-V multiple bond and [ [HC(NCy)2 V(/i-Cl)l2 which is also dimeric (Scheme 107). The formation of V2[HC(NCy)2l4 was shown to proceed through the intermediate monomeric [HC(NCy)2l2V(TMEDA), which was isolated and fully characterized. The dinuclear structure was reversibly cleaved by treatment with pyridine forming the monomeric [HC(NCy)2l2V(py)2. ... 

Mohamed, A.A., Abdou, H.E. and Fackler, J.P. Jr (2006) Mercury(ll) cyanide coordination polymer with dinuclear gold (1) amidinate. Structure of the 2-D [Au2(2,6-Me2-formamidinate)2]-2Hg (CN)2 2THF complex. Inorganic Chemistry, 45, 11-12. 

Bicyclic structures of this type are more reactive than monocyclic or acyclic carbamates, indicating that a relatively rigid orientation of the carbonyl group is favorable to lithiation. Substituted formamidines can also be lithiated.60... 

A few linear tetranuclear complexes of ligands related to dpa have been structurally characterised, namely [Ni4(phdpda)4] (phdpda = dianion of A-phenyldipyridylamine),39 [Cu4(dphip)4]2 + (dphip = anion of 2,6-bis(phenylamino)piperidine),37b and [Cr4(dpf)4Cl2]2+ (dpf = anion of bis(2-pyridyl)formamidine),38 but no pertinent electrochemical investigation is available. 

Amidines. After the initial observation that formamidines are agonists for OA receptors in the firefly (14,15 58), these compounds have been shown to mimic OA in virtually every insect system known to contain OA receptors, including the DUMETi system (59)f the glandular lobe of the corpus cardiacum (60) and the fat body ( ) of the locust, and various CNS adenylate cyclase preparations (26-28). The structure-activity relations of amidines as octopaminergic agonists have been examined in several systems including adenylate cyclase stimulation in the firefly lantern and... 

The direct reaction of [TCO4] in ethanolic solution with dppe and oxalic acid produces the red Tc" complex [Tc(ox)(dppe)2] (552). Attempts to prepare similar complexes with succinic acid, phthalic acid, or salicylic acid failed, or the complexes were stable in solution only. " Similarly, cationic complexes of Tc" are produced by reaction of the versatile precursor [TcO(OH)(dppe)2] (204) with various dithiocarbamates, which produces several complexes of general formula [Tc(dtc)(dppe)2] (553). For this reaction the reductant formamidine sulphinic acid (510) was required in an alkaline solution. The X-ray crystal structure of [Tc(S2CNMe2)(dppe)2] (554) shows a distorted octahedral geometry. Cyclic voltammetry reveals a reversible reduction wave Tc"/Tc couple at —0.53 V, and a reversible oxidation at +0.3 V for the Tc" /Tc" couple. The same compound (554) was also prepared from the thiourea precursor [TcO(tmtu)4] + (91).The reaction of this precursor in dmf in the presence of dppe produced a mixture of brown [TcO(dtc)(tmtu)2] and the Tc" complex (553). The first compound is probably an intermediate... 

Azzaroni etal. [163] have used STM to study electrochemical reactivity of thiourea toward Au(lll). Sequential STM imaging has shown that thiourea adsorbs as striped arrays that evolve to the hexagonal close-packed structure when surface charge density is decreased. The transient hep structure undergoes electrooxidation to formamidine disulfide, which slowly yields adsorbed sulfur. Adsorption of thiourea on the pc-Au electrode from KCIO4 solutions has also been studied [164]. The film pressure and the Gibbs surface... 

At the moment we do not have a convincing explanation for the observed influence of the inhibitor structure. The basicity can not account for the effect of the substituents because both the more basic guanidine and the less basic N,N -diphenyl formamidine are less selective than formamidine itself. 

Here we revisit the VB resonance model in formamide by taking all six resonance structures into account. Such a study allows us to compare the individual contributions from resonance structures 1-6 to the resonance effect in formamide. For comparison, the isoelectronic systems vinylamine and formamidine are also investigated to gain insights into the trends of resonance stabilization. A 6-31G(d) basis set is employed in the calculations, and the orbitals in the VB functions are self-consistently determined for each resonance structure, but restricted to be atomic orbitals. The structural weights of the six resonance structures are listed in Table 2. 

Four quadruply bonded Cr(II) complexes, [Cr2(formamidinate) (acetate)4 ] (n = 2 4), have been structurally characterised and exhibit Cr-Cr bond lengths in the range 1.8897(5) to 2.012(1) A, with distances dependent on the presence (long) or absence (short) of axial interactions.7 The heterotrinuclear complex [Cr2Fe(dpa)4Cl2] (dpa = 2,2 -dipyridylamide) incorporates a quadruply bonded Cr2 unit into a linear Cr-Cr Fe framework, with electrochemical studies showing a dramatic stabilisation of the higher iron oxidation states.8... 

Aminomethyleneamino-thiopyrylium (100) (75EGP113911) and -sele-nopyrylium (101) salts (77EGP123527, 77T731) have been prepared by heating formamidine derivatives 99 and /3-aminovinylthioketones 97 or selenoketones 98, respectively (Scheme 6). In structures 100 and 101,... 

Potentially bidentate ligands, such as the formamidinates [RNCR NR], the monoanion derived from 2,6-bis(phenylamino)pyridine and 7-methyl-l,8-naphthyridin-2-one, and others, formed complexes with a paddle wheel structural motif. Figure 5(d), and some of these complexes could be oxidized by ferrocenium cations to give mixed-valent species. Generally, such oxidation led to a slight lengthening of the metal-metal bond. 

The action of ammonia, primary and secondary amines on alkoxymethyleneiminium salts or alkylmercaptomethyleneiminium salts affords amidinium salts. Provided the educts are chosen in such a manner that the substitution pattern of the resulting amidinium salts does not exceed that of A/jV.AT -trisubstituted salts, the amidines can be released from the salts by addition of bases (see also Section 2.7.2.5.3). Very often the alkoxymethyleneiminium salts were prepared in situ and reacted without further purification with the amino compound to give the desired amidine. This amidine synthesis is of special synthetic interest, since it was stated that formamidines, derived from alicyclic amines, e.g. (306 equation 164), which are simple to obtain by this method, are readily transformed to reactive carbanions. Heterocycles, e.g. (307 equation 165), containing amidine structures, are accessible by reaction of appropriate difunctional compounds with iminium salts. ... 

Synthesis of Formamidines. N-(Benzylideneamino) heterocycles structurally transform into formamidines by inversion of the azomethine linkage. A series of formamidines related to l-(benzylideneamino)-imidazolidin-2-ones has been prepared by reaction of substituted formanilides with imidazolidin-2-one (ethylene urea) in thionyl chloride solution. The one-pot method which involves condensation between ethylene urea and an imidoyl chloride, represents a new method for the synthesis of trisubstituted formamidines (Chart VI). 

Formula 175 represents the incorrect planar structure proposed by Brindley and Pyman 147) in 1927 for emetine (1). In this connection, Harada et al. 148) synthesized the four stereoisomers possible for ( )-C-noremetine Pyman [( )-176] and isolated them in the form of hydrobromide salts. Takacs and Boito 149) synthesized the (-)-tricyclic alcohol 177, a one-carbon homolog of the Alangium alkaloid (-)-protoemetinol (34), from the chiral formamidine 117 in 36% overall yield via a five-step route proceeding through the stereoselective iron-catalyzed cyclization of the key intermediate 178. 

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