Action des halogenures d'alkylmagnesium sur les pyrones-2—VI : Etude de la regioselectivite de l'ion enolate intermediaire de la reaction

Grignard reagents normally react with 2H-pyrones to yield unsaturated ketols, dihydropyranols, dienones and 2H-pyrans. In some cases, products are obtained by attack on the most sterically crowded position of the enolate ion. Since steric hindrance is an unsatisfactory basis for predicting the reactivity, we have applied a theoretical study to this problem. The model used is based on an enlarged electronic delocalization in the transition state, and allows the interpretation of the regioselectivity of the reaction.     

Etude des reactions des diazoderives avec les cycloimmonium ylures-I : Action des sels de diazonium sur quelques pyridinium - ylures

The synthesis of cycloimmonium salts of the type $\text{7}$, $\text{8}$ and the corresponding cycloimmonium ylides $\text{9}$, $\text{10}$ are reported. In the reaction with diazonium salts $\text{11}$, $\text{12}$ the pyridinium monosubstituted carbanion ylides $\text{9}$, $\text{10}$ give the pyridinium disubstituted carbanion ylides $\text{17}$ – $\text{20}$. These are new types of isolable stable ylides. The synthesis involves the formation “in situ” of ylides $\text{9}$, $\text{10}$ which are bonded by their nucleophile ylide carbon atom to the nitrogen atom in diazonium salts. The intermediat formation of cycloimmonium salts $\text{13}$ – $\text{16}$ must be accepted. The structures of all compounds presented in this paper have been established by using elementary analysis, IR and ¹H-RMN spectra.     

Action des halogenures d'alkylmagnesium sur les pyrones-2—V : Action de l'iodure de methylmagnesium sur des alkylpyrones-2 non substituees en position 4

To check if only 4-substituted 2-pyrones lead to 2H-pyrans with Grignard reagents, the reactions of 4-unsubstituted 2-pyrones with methylmagnesium iodide have been studied. From 3, 5, 6 trisubstituted 2-pyrones, 2H-pyrans may be obtained; but 5,6-disubstituted 2-pyrones give only linear products.     

Action des reactifs de grignard sur les dithioesters : Addition carbophile d'organomagnesiens insatures. synthese de cetones β-ethyleniques

Reactions of allyl, benzyl, propargyl and vinyl Grignard reagents with methyl dithioacetate give dithioacetals (or hemidithioacetals) resulting from a carbophilic addition process. Reactions with various allylic organomagnesium compounds always involve an “inversion” of the allylic chain and direct carbophilic addition, rather than initial thiophilic addition followed by [2.3] sigmatropic shift. Three methods for the synthesis of β-unsaturated ketones are described, showing the potential synthetic uses of the reactions of Grignard reagents with dithioesters.     

Action du methyltri(n-butyl)fluorophosphorane sur les halogenures et les sulfonates d'alkyle

Monofluorophosphoranes R₃MePF are used in exchange reactions to prepare monofluorinated organic compounds. Tri(n-butyl)methylfluorophosphorane (n-Bu₃MePF), easily available, is the most reactive. In solvents of low polarity or even in non-polar solvents, it reacts at ?70° with alkyl sulphonates and halides activated by ester, ketone, or ether functions. Thus, fluorinated epoxides can be obtained directly by exchange from their chlorinated or brominated homologues.     

Additions electrophiles sur les esters acetyleniques et alleniques—IV : Addition des halogenes et des halogenures de sulfenyle sur le butyne-3 oate d'ethyle

Ethyl but-3-ynoate undergoes electrophilic additions of BrCl and of ICl to give CHXCClCH₂COOEt E (X = Br or I). The addition of sulfenyl halides RSY follows the opposite orientation and leads to CHYCSRCH₂COOEt E (Y = Cl or Br, R = Et or Ph). In the case of IBr, both CHICBrCH₂COOEt E and CHBrClCH₂;COOEt E are obtained.A mechanistic interprétation of these results is supported by both the orientation and the kinetic order of the addition: PhSCl reacts by an Ad_E2 process, whereas ICl addition involves a combination of Ad_E3 and Ad_E4 mechanisms.     

Etude de l'action des alkylmagnesiens primaires et arylmagnesiens sur les anhydrides tricycliques pontes

The reaction of primary alkyl and aromatic Grignard reagents with bridged tricyclic di-carboxylic anhydrides gives the corresponding dialkylated tricyclic lactones via di-addition process. The lactones were transformed by retro-Diels-Alder reactions into 4,4-dialkylated butenolides.     

Etude par RMN 1H des effets de solvant sur les déplacements chimiques et les couplages vincinaux des benzothiénopyridines

The solvent/solute interactions of four isomeric benzothienopyridines (parent compounds) have been investigated by ¹H n.m.r. A close study of the second-order spectra shows: (i) a preferential orientation of the solvent molecules (acetone) surrounding the pyridine ring; (ii) large variations in the coupling constants of the benzenic part of the benzothienopyridines as a function of the solvent; (iii) a preferential interaction of the pyridine ring in collision complexes with benzene. These results can be applied to a comparative study of the complexes between DNA base pairs and intercalating derivatives.     

Etude dans la serie des organostannylazoles : II. Reactions de substitution nucleophyles avec les halogenures d'alkyles

Reactivity of organotinamines of pyrazole, imidazole, 1,2,4-triazole and benzotriazole towards alkyl halides has been studied. Primary halides give the corresponding N-alkylated heterocycles in quantitative yield. Reactivity decreases with secondary and tertiary halides. A mechanism is proposed for these reactions.     

Action de l''hydroxylamine, de l''hydrazine et de ses derives sur les γ-pyrones

The reaction of hydroxylamine and hydrazine on γ pyrones was generally reported to yield various heterocycles in which nitrogen is incorporated. More recently, several authors have reported that γ-pyrones oximes and hydrazone derivatives can be obtained and have settled some controversial previous results. This report presents a review of this question.     

Etude des aldimines lithiees : III. Action des epoxydes et synthese d'amino-2 et d'hydroxy-2 tetrahydrofurannes

The reaction of lithiated aldimines, prepared from activated amides, with epoxides leads to good yields of 2-aminotetrahydrofurans (neutral hydrolysis) and 2-hydroxytetrahydrofurans (acid hydrolysis). Various epoxides were examined.     

Reaction du gem-chloro(methyl)allyllithium sur les aldehydes et les cetones: nouvelle methode de synthese d'epoxydes α-ethyleniques tri-et tetra-substitues

Tri- and tetra-substituted epoxides are easily prepared by treating gem-chloro(methyl)allyllithium with aldehydes and ketones.     

Action des composes organomagnesiens sur les pyrones-2-VII : Etude de la stabilite relative des hydroxy-6 dihydro-5,6 2h-pyrannes et des cetols tautomeres correspondants

In the reaction between organomagnesium compounds and 2-pyrones, the relative stability of the 6-hydroxy 5,6-dihydro 2H-pyrans and their tautomeric forms (ketols) has no influence on the reaction pathway. When ethylenic ketols are obtained, the corresponding tautomeric dihydropyranols are prepared in a selective way by reaction of nucleophilic reagents on the 3,6-dihydro-2-pyrones. In the other hand, the exclusive formation either of the dihydropyranols or of the unsatured ketols E, during these two reactions, shows up that here is no equilibrium between these two entities in the experimental conditions.     

Influence des interactions de torsion dans les reactions d'addition sur les cyclohexanones. interpretation generale du deroulement sterique des reactions des hydrures ou des organomagnesiens sur les cyclohexanones

The addition of allyl and butenyl Grignard reagents to 4-t-butylcyclohexanone affords a greater proportion of the equatorial alcohols than is formed from the corresponding saturated Grignard reagents (propyl and s-butyl). In the case of the allyl Grignard reagent, the equatorial alcohol is the major product. Lithium aluminium hydride reduction in ether at 0° of cis and trans 4-t-butyl-2-methyl-cyclohexanone and cis and trans 4-t-butyl-2-chlorocyclohexanone affords mixtures of epimeric alcohols in ratios of equatorial to axial OH 8.4:1, 20:1, 4.2:1, and >70:1 respectively. These results fit in well with the view that polar interactions and torsional strain are both important in determining the steric course of the reaction.     

Etude dans la serie des organosilylazoles : I. Action des halogenures d'alkyle,des chlorures d'acide et des cetones halogenees

The reactivity of organosilylamines of imidazole, pyrazole, 1,2,4-triazole and benzotriazole towards alkyl halides, acidic chlorides and halogenated ketones has been studied. Except for 1-trimethylsilylimidazole, which gives a mixed quaternary salt, reactions with primary halides lead to the corresponding 1-alkylated heterocyclic compounds in high yields; in each case only one isomer is obtained (1-alkyl-1,2,4-triazole and 1-alkylbenzotriazole). Similarly acidic chlorides give 1-acylated derivatives in quantitative yields. Finally α- or β-halogenated ketones show different behaviour and give the addition or substitution products.