Formamidines cyclic

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... 

Azirine derivatives 318 were shown in the same article to be precursors of triazines 324 (30-35% yield) and pyrimidines 326 (30% yield) upon treatment in DMSO with guanidine and formamidine, respectively (Scheme 71). A similar pathway to that outlined above is also invoked to explain these results thus, intermediate 323 would yield 324 by electro-cyclic ring closure, whereas 326 would be formed by heterocyclization of 325 and loss of ammonia (91JOC7). 

Acy 1-4-amino-1,5-dihydro-2-pyrrolones (6) (type Z in Scheme 1) possess the features of cyclic enaminediones. The push-pull-7r system decreases the nucleophilicity of the amino group. Therefore N-acylation with carboxylic acid chlorides requires relatively drastic conditions (dioxane, 100°C, K2C03). In particular, the reaction of the highly reactive DMF-acetal 8 to formamidine 9 succeeds only while refluxing in benzene (87TH1). (See Fig. 3.)... 

The cycloaddition of methyl acrylate with 7V-thiobenzoyl-7V,7V-dimethylformamidine 363 under pressure affords the 4-dimethylamino-5,6-dihydro-4//-l,3-thiazine 364. On treatment with methyl iodide and triethylamine, 364 eliminates trimethylamine to give 6//-l,3-thiazine 365 which can also be obtained directly through the cycloaddition of methyl acrylate and the methiodide salt of the formamidine <1987SC1971>. The same methodology has been extended to other 1,3-thiazines by varying the formamidine or electron-deficient cyclic dienophile (Scheme 170) <1988SUL205>. 

Unlike the analogous isocyanide Au complexes, which react with alcohols or amines to form carbenes, the Ag complexes rearrange to the formamidate (RN=CHOR ) or formamidine (RNHCH=NR ) species, which are all probably cyclic oligomers such as (4). 

The stimulation of the octopaminergic nervous system of invertebrates is a proven strategy for the control of important pest species. This has been achieved in the past by the use of octopamine receptor agonists such as formamidine and imidazoline derivatives. However, other potential strategies to achieve this end include the inhibition of cyclic nucleotide phosphodiesterase, inhibition of the neural reuptake of octopamine, and inhibition of octopamine N-acetyltransferase. Using the American cockroach nervous system, formamidines were found to inhibit both the uptake and acetylation of octopamine, but not with a potency comparable to their effect on octopamine receptors. The tricyclic antidepressant, desipramine, and the benzylamine, xylamine, were the most active inhibitors of these octopamine removal systems. The pharmacological profiles for uptake and N-acetylation appear to be quite similar, but differ from that of the adenylate cyclase-linked octopamine receptor. 

Hie cyclic anhydride (80.4) reacts with trimethylsilyi azide under anhydrous conditions to give a mixture of I,3-oxazine-2,6-dione isomers, which was used without further purification to synthesis several extended purines. Reaction with formamidine acetate in DMF in effect replaced the furandione ring by a pyrimidinone. Cyanamide produced a new fiued 2-aminopyrimidin-4-one [in (80.5, R = NH )], while urea led to a pyrimidinedione. Isatoic anhydride similarly yields 2-aminoquinazolin-4-one on treatment with cyanamide-DMF. 

Chiral cyclic allylic amines have also been utilized in lithiation-substitution reactions to access substitution a to nitrogen. Meyers and coworkers have demonstrated that lithiation of chiral formamidine-protected pyrroline 135 and tet-rahydropyridine 136 followed by substitution with electrophiles provides both the a and y-substituted heterocycles (Scheme 43) [97]. 

Dynamics in the solid state include processes of an intramolecular proton transfer the tautomerism of porphyrin [10] or the intramolecular proton transfer in cyclic AW-bisaryl formamidine dimers [11] was studied by means of CP MAS NMR. 

Formamidines from hydrogen cyanide Cyclic formamidines... 

Formamidines s. 10, 329 cyclic amidines from lactams, 4-amino-l,5-benzo-diazepines, s. A. Bauer et al., J. Med. Chem. 16, 1011 (1973)... 

Meschede, L., Limbach, H-H. (1991). Dynamic NMR Study of the Kinetic HH/HD/DD Isotope Effects on the Double Proton Transfer in Cyclic Bis(p>-fluorophenyl)formamidine Dimers. J. Phys. Chem., VoL95, p>p. 10267-10280 Michaelis, L. Menten, M.L., (1913). Die Kinetik der Invertinwirkung. Biochemisches Zeitschrift, Vol. 49, pp. 333-369. 

For instance, the metalation-alkylation of cyclic formamidines such as 425 can be used for introducing two on-ring methyl groups with high bis-equatorial selectivity to form 427 via 426 [133]. If, however, urethanes 428 are used for activation, the... 

Based on PES calculations on the isolated complexes, the existence of further cyclic ion pairs has been suggested, among them for ammonium salts of zeolite-clusters or ammonium tetrafluoroborate (Ref.46, 3-21G and 6-3IG ab initio basis sets). In these cases, an asymmetric hydrogen bonded form did not occur as a second minimum on the PES. Surprisingly, the proton transfer in the eight-membered formamidine dimer is supposed to pass a transition structure of lower symmetry to form an ion-pair like intermediate... 

Proton removal adjacent to a heteroatom is further facilitated if the lithium can be internally coordinated to proximate electron donors, such as the carbonyl oxygen, permitting the formation of dipole-stabilized carbanions. Thus lithiations of various amides, thioamides, imides, esters, Boc derivatives of cyclic amines (pyrrolidines, piperidines, and hexahydroaze-pines), thioesters, )V,iV-dialkylthiocarbamates, and various formamidine derivatives are achieved conveniently using s-BuLi (eqs i3 i7) 32,43b.44.47a,48a Subsequent addition of electrophiles followed by hydrolytic removal of the activating carbonyl, carbamoyl, or formamidine moiety provides a valuable synthetic route to a variety of a-substituted amines, alcohols, and thiols. Successful alkylation of the dipole-stabilized car-banions may require the conversion of the initial lithio carban-ions into their organocuprate derivatives, e.g. by the addition of n-PrC=CCu. ... 

Formamidine is another species known for detailed study of its interaction with several water molecules [70]. The cyclic mono-, di- and trihydrated complexes have been studied to evaluate the performance of a number of the DFT approximations, comparing with Moller-Plesset theory. The outcome of this study is the conclusion about the similar accuracy in the calculation of the energetic properties of the hydrated complexes at the MP2/6-31(d,p) and DFT(BH H-LYP/6-31(d,p)) levels of theory. 

Meyers has investigated the conversion of jS-carboline derivatives to penta-cyclic yohimbines initially in methodology studies and then in target oriented investigations. In their preliminary efforts, Meyers and his coworkers converted tetrahydro-jS-carboline 402 to formamidine 403 (Scheme 3.69) (118). Alkylation of the lithio-anion of 403 followed by removal of the formamidine moiety and subsequent acid induced lactamization afforded 406 which possesses the pentacyclic yohimbine skeleton. 

Dynamic NMR study of kinetic HH/HD/DD isotope effects of double proton transfer in cyclic bis(p -fluorophenyl)formamidine dimers. /. Phys. Chem., 95,... 

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