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The synthesis of novel substituted pyrroloquinolinones is described by concomitant ring contraction cyclization form 2-(2-amino-5-nitro-phenyl)-[4 H ]-1,3-thiazines, which were derived from N -substituted 5-nitro-anthranilonitrile. An easy access to novel 4-thiono-1,4-dihydro-1,3-quinazoline heterocycles is also mentioned.

The preparation of 2-phenyl-4-dimethylamino-1-aza-, 1-oxa-, 1-thia-, 1-selena-3-azabuta-1,3-dienes as well as their 4-methyl derivatives is described following a new heteroatom interchange reaction process. Heteronucleophilic attack at one particular reactive site of bis-electrophilic amidinium salts is the key feature of the process. In addition, we also disclose that the substituted 1-oxa-3-aza- and 1,3-diazabuta-1,3-dienes can be obtained by a reactional transformation cascade initiated by either silver acetate addition or tosyl azide [3+2] cycloaddition onto the CS or CSe double bonds of the 1-thia- and 1-selena-3-azabuta-1,3-diene analogues.

A new synthesis and the reactivity of stable selenaazadienes are discussed. Their dienic, electrophilic and nucleophilic character are used to prepare five and six membered selenoheterocycles. The easy access to selenazine, selenazinone, selenopyran, selenazoline, selenazole and selenophene heterocycles from N-selenoacylamidines is described. An interpretation of the reactivity of the selenaazadiene systems, experimentaly compared to their thia analogues, is based on their physico-chemical parameters and correlated to the theoretical calculations of their frontier molecular orbital energy levels.

An original synthesis of substituted formyl selenophene heterocycles is described via selenoamide vinylogue from N-selenoacylamidines. The access of mono and bis-substituted 1,3-dithiol-2-ylidene selenophenes, potential π-conjugated precursors of selenafulvalene analogs, was achieved using Wittig olefination.

New 2-aza-1,3-dienes bearing 1 and 3-donor substituents are prepared from N-thioacylacetamidines through deprotonation of N-ylidene acetamidinium iodides. The 2-aza-3-(dimethylamino)-1-(methylthio)-1-phenylbutadiene (3) is trapped in situ by the residual precursor salt acting as a heterodienophile to give the pyrimidine 5. Substituted 2-aza-1-(dimethylamino)-3-(methylthio) analogues react readily with a variety of electron-deficient dienophiles to yield pyridine or pyrimidine derivatives. The stereochemistry of the hetero Diels-Alder reaction in the cases of dimethyl fumarate and acrylonitrile has been assigned by X-ray diffraction analyses of the resulting tetrahydropyridines and corresponds to an exo selectivity. The number and nature of cycloadducts in the cases of dimethyl acetylenedicarboxylate and phenyl isothiocyanate depend on C-4 substitution. The results obtained from the C-4 unsubstituted azabutadiene 8 are explained by an allylic rearrangement involving the 1,3-migration of dimethylamino group in the primary [4+2] adduct.

N′-selenoacylamidines were isolated by condensation of selenobenzamide with orthoamides. [4+2] cycloadditions with electrophilic dienophiles were performed leading to 1,3-selenazine derivatives. Selenoamide vinylogs obtained by thermolysis of 4 H -1,3-selenazines, were the precursors of functionalised selenopyrans or selenophenes.

Electrochemical and chemical reductions are complementary methods for the selective hydrogenation of 2-substituted-6-methoxycarbonyl-4H-1,3-thiazine-4-ones leading to 2,3-dihydro; 5,6-dihydro- and 2,3,5,6-tetrahydro-4H-1,3-thiazine-4-ones without ring opening and ketone function alteration. Selective hydrogenation of the imine bond (C[dbnd]N) or the alkene bond (C[dbnd]C) depends on the nature of the heteroatomic substituent [(CH3)2N, C2H2O, C6H5CH2S] at the 2 position. La reduction par voie electrochimique (a potentiel controˇle et sur cathode de mercure) et par voie chimique (borohydrures, hydrure de tributyletain, hydrure de triethylsilane, aluminium amalgame) des 6-methoxycarbonyl-4H-1,3-thiazine-4-ones substituees en position 2 par un groupement aromatique ou heteroatomique permet l'obtention selective des 2,3-dihydro; 5,6-dihydro- et 2,3,5,6-tetrahydro-4H-1,3-thiazine-4-ones correspondantes, sans ouverture du cycle thiazinique ni alteration de la fontion cetonique. L'orientation de la reduc...

Selective reduction of 4H-1,3-thiazine-4-ones leads to new substituted 6H-1,3-thiazines. The isomerisation from 6-to 5-methoxycarbonyl-6H-1,3-thiazines via substituted 4-acetoxy-1-thia-3-aza-butadienes by a cycloreversion-cycloaddition process can be performed in one step.

The thioamide vinylogues (2-aminovinyl thioketones) react as heterodienes with open-chain and cyclic dienophiles to give substituted 4-amino-3,4-dihydro-2H-thiopyrans, or substituted 2H-thiopyrans and substituted 7 - methyl - 7,7a - dihydro - 5H - thiopyranno[2,3 - c] - 5 - furanones respectively, in good agreement with calculated perturbation energy of second order.

(4+2)cyclocondensation reactions under high pressure between methylacrylate and 2-substitutes 1-thia 3-aza 4-aminobutadienes leads selectively to 2-substituted 5-methoxycarbonyl 6H-1,3-thiazines.

2-Phenyl-4-dimethylamino-1-thia-3-azabutadiene and methylacrylate gave 5,6-dihydro-4H-1,3-thiazine by 4 + 2 cyclocondensation reaction at 55°C. The heterodienes configuration was established by X-Ray spectra. The Diels-Alder character of this reversible reaction was indicated by kinetic and thermodynamic parameters determined by 1H N.M.R.