Trifluoromethylation of enamines under acidic conditions

A method for the trifluoromethylation of enamines using Me₃SiCF₃ leading to α-CF₃-substituted amines is described. The reaction is promoted by hydrofluoric acid generated from KHF₂ and either trifluoroacetic or triflic acid, and involves protonation of the enamine followed by transfer of the CF₃-carbanion from the silicon reagent to the cationic electrophile.     

Reaction of enamines with trifluoromethyl containing carbonyl reagents

The reaction of linear push-pull enamines bearing a methyl group at the α-position with a set of trifluoromethylated carbonyl compounds was investigated. It has been found that the reaction proceeds at the methyl group of the enamines. The first computational study of the reaction between push-pull enamines and strong electrophilic reagents was reported. Out of three pathways considered DFT and MP2 calculations support ene-mechanism previously suggested based on experimental results only.     

Reactions of <Emphasis Type="Italic">N</Emphasis>-arylsulfonylquinone imines with enamines

Depending on the reaction conditions N-arylsulfonyl-1,4-quinone imines with enamines led to the formation of the products of 1,4-addition, derivatives of benzo- and naphthofuran, indole, and benzindole.     

Reactions of cyclohexanone enamines with asymmeric diimides

Tetrasubstituted enamine derivatives which rearrange into 1,3,4-oxadiazine isomers have been isolated from aryl acyl diimides and 1-morpholinocyclohexenes. The same reactions with 1-pyrrolidinocyclohexenes have led directly to the cyclic derivatives.     

Reactions of benzimidazole-2-carbaldehyde with enamines

Benzimidazole-2-carbaldehyde reacts with 1-morpholinocyclohexene, 1-morpholinocyclopentene, and aminocrotonic ester upon heating to form 4a,11-dimorpholino-1,2,3,4,11,11a-hexahydro-4aH-indolo[1,2-a]benzimidazole, 2-(2-morpholino-4,5-dihydrofulvenyl)benzimidazole, and 4-(benzimidazol-2-yl)-3,5-diethoxycarbonyl-2,6-dimethyl-1,4-dihydropyridine, respectively. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 566–571, March, 1999.     

The chemistry of polycyclic arene imines. V. Reactions of phenanthrene 9,10-imine with nucleophiles under phase transfer conditions

Reactions of phenanthrene 9,10-imine (1) with alkyl halides, sodium azide and ammonium thiocyanate in two liquid phase systems were investigated. In the presence of aqueous sodium hydroxide and alkyl halides triethylbenzylammonium (TEBA) salts promote N-alkylation of 1 with preservation of the aziridine ring. Tetrabutylammonium (TBA) salts catalyze nucleophilic substitutions in which the three membered ring is cleaved. Aqueous sodium azide reacts with 1 to give trans-10-azido-9,10-dihydro-9-phenanthrenamine (2) . Ammonium and potassium thiocyanate cause expansion of the aziridine ring; while the unsubstituted imine 1 yields the 2-thiazolamine derivative 4 , N-butylphenanthrene 9,10-imine (8) froms trans-3a,11b-dihydro-3-butylphenanthro[9,10-d]thiazol-2-imine (9) with an exocyclic CN bond. The structure of 9 was established by X-ray crystal analysis.     

Condensation of homophthalic anhydrides with heterocyclic imines and DMAD under mild conditions

Condensation of 7-methoxyhomophthalic anhydride with 2-imidazoline, 2-thiazoline, 2-oxazoline, 1-pyrroline trimer and DMAD (with triethylamine) occurs rapidly under mild conditions.     

Reactions of 1,3,3,3-tetrafluoro-2-methoxycarbonylpropenesulfenyl chloride with enamines

1,3,3,3-Tetrafluoro-2-methoxycarbonylpropenesulfenyl chloride readily reacts with enamines (derivatives of -oxo acids) to give sulfenylation products. The reactions with N-aryl-substituted enamines are accompanied by cyclization to form N-aryl-2-(2,2,2-trifluoro-1-methoxycarbonylethylidene)-2,3-dihydrothiazoles.     

Reactions of 4-morpholino-1,2-naphthoquinone with enamines ando-phenylenediamine

The reactions of 4-morpholino-1,2-naphthoquinone with enamines, cyclohexanone derivatives, afford 7a-amino-5-morpholinohexahydrobenzo[b]naphtho[1,2][1,4]dioxines, while the reaction witho-phenylenediamine yields 5-morpholinobenzo[a]phenazine. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 729–732, April, 2000.     

Substitution reactions at silicon under strongly acidic conditions: Ligand metathesis between methyltrichlorosilane and octamethylcyclotetrasiloxane

A study of the reactions between methyltrichlorosilane (MeSiCl₃) and octamethylcyclotetrasiloxane (D₄) in the presence of trifluoromethanesulfonic acid (HOTf) showed that nucleophilic substitution in CHCl₃ solution at the trifunctional silicon was surprisingly slow in comparison with the rate of equilibration/polymerization of D₄. The reaction rate at MeSiCl₃ was significantly faster with water present and faster still in THF. In these reactions, there was no evidence for SiOH groups (²⁹Si NMR), even in the presence of excess water. The overriding criterion for relative reactivity toward nucleophilic substitution under strongly acidic conditions is the relative leaving group ability of the groups on silicon. Once MeSiCl₃ begins to participate in the redistribution reactions, mono- 3 and tri- 5 , but not di-substituted 4 systems are formed (MeSiCl_3−x(D_nSiMe₂Z (Z = OTf, Cl))_x, x = 1, 3), likely through an intramolecular reaction. The mechanisms of nucleophilic substitution at silicon under these conditions are discussed.     

The origin of the stereoselectivity in the asymmetric Michael reaction using chiral imines/secondary enamines under neutral conditions: a computational investigation

The diastereoselectivity in the asymmetric Michael reaction using chiral imines/secondary enamines under neutral conditions has been investigated with the help of AM1 calculations. The energetic differences between the two competing transition states involving enamino ketones 7d, 7g and methyl acrylate are in good agreement with the stereoselectivities observed with the corresponding chiral imines, derived from 1-phenylethylamine (de 95%) and from 1-cyclohexylethylamine (de 45%). The calculated transition structures indicate that steric factors govern the π-facial discrimination.     

Acylation of phosphoryl- and thiophosphorylacetonitriles under phase transfer catalysis conditions and the keto-enol tautomerism of phosphorus-substituted acylacetonitriles

A procedure was developed for acylation of phosphoryl- and thiophosphorylacetonitriles under phase transfer catalysis conditions. The reaction in the solid KOH/MeCN system affordedC-acylation products in high yields. In the individual state and in aprotic solvents, these products exist in the enol form (Z isomers) stabilizedvia a strong intramolecular hydrogen bond. In hydroxyl-containing media and in aprotic bipolar solvents, these compounds exist as a mixture of two geometric isomers (E andZ) of the corresponding enols. In this case, theZ isomer exists in two forms, namely, in the cyclic form with an intramolecular hydrogen bond and in the open form stabilized by intermolecular hydrogen bonds with the solvent. The results of X-ray diffraction analysis of both forms ofZ isomers of the compounds containing the phosphoryl and thiophosphoryl groups are discussed. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1687–1694, September, 1998.     

Reactions of benzonitrile oxide with fluoroketones and their imines

Conclusions Fluoroketones (I) and their imines (III) enter into a noncatalyzed addition reaction with benzonitrile oxide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1916–1918, August, 1968.     

Synthesis of the new adducts of imines and enamines with PH acids and their derivatives

Nucleophilic or radical addition of esters of trivalent organophosphorus acids with PH fragments to various imines and enamines is proposed as convenient methods for the synthesis of new substituted aminomethyl organophosphorus compounds with three‐, four‐, and five‐coordinated phosphorus. Also the new functionalized derivatives of these compounds with acyl and methanesulfonyl moieties are synthesized, and some properties of the obtained compounds are presented. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:70–80, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20513     

Reactions of methylchlorodisilanes with Grignard reagents

Reactions of Cl₂MeSiSiMeCl₂ with RMgCl make it possible to obtain and isolate pure disilanes containing a smaller number of functional groups, namely, RMeClSiSiMeCl₂ (R = Ph), RMeClSiSiMeRCl (R = Prⁱ, Ph), and R₂MeSiSiMeRCl (R = Buⁱ). The reaction of Cl₂MeSiSiMeCl₂ with BuⁿMgCl is the least selective. The chlorides obtained were reduced with LiAlH₄ into the corresponding hydrides.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 954–957, May, 1995.     

Mechanistic analysis of the transition metal-catalyzed hydrogenation of imines and functionalized enamines

The asymmetric hydrogenation of prochiral imines has been mainly studied on cationic rhodium or iridium complexes and involves the coordination of the nitrogen atom on the metal centre. Oxidative addition of dihydrogen followed by one hydride transfer onto the carbon atom produces a σ-bonded nitrogen-metal intermediate from which reductive elimination occurs with the second hydride to produce the amine. From all these reactivity studies we propose that in an early step a hydrogen atom transfer could occur on the nitrogen atom to generate an iminium species which coordinates the metal centre through the CN double bond. The Shvo catalyst, an active neutral ruthenium(II) complex, presents the particularity to transfer almost simultaneously a proton from the hydroxycyclopentadienyl ligand and a hydride bonded to the metal center. In this case too, we suggest the first proton transfer generates an iminium species.Morever, a few titanium complexes have been shown to catalyze the hydrogenation of imines.Concerning enamines, literature is rather scarce on catalytic success. On the contrary, many studies focused on hydrogenation of enamides, which represent functionalized enamines, and enantiomeric excesses very close to 100% have been obtained. Extensive studies of the effect of the (chiraldiphosphine)Rh⁺ framework on the asymmetric induction have shown that several reversible steps can occur related to the oxidative addition of dihydrogen before or after the coordination of the enamide; the irreversible step directly connected to the asymmetric induction is the formation of the chiral alkyl-rhodium species.