Deamination of the amino acid fragment in imine metallacycles: unexpected synthesis of an NH-aldimine organometallic compound

We report that the action of Lewis bases, such as triphenylphosphine, pyridine, or trimethylamine, on imine metallacycles derived from amino acids leads to the formation of the first organometallic compound of an NH aldimine, a highly reactive organic species, and the corresponding alpha-ketoester, in a deamination reaction that mimics the metabolism of alpha-amino acids. The synthesis of different cyclopalladated compounds by a reaction between palladium acetate and the Schiff bases 2,4,6-Me(3)C(6)H(2)CH=NCH(R(1))COOR(2) (R(1) = CH(2)Ph, R(2) = Et and R(1) = Ph, R(2) = Me) is also reported.     

An unexpected highly diastereoselective double Baylis-Hillman reaction of per- (or poly)fluorophenyl aromatic aldimines with methyl vinyl ketone

Aza-Baylis-Hillman reaction of per- (or poly)fluorophenyl aromatic aldimines 1 with methyl vinyl ketone (MVK) was studied. It was found that both the used Lewis base and solvent can significantly affect the reaction. Using triphenylphosphine as a Lewis base, the reaction of 1 with MVK proceeded smoothly to give the normal Baylis-Hillman adduct 2 along with the double Baylis-Hillman adduct 3 as by-product in THF. When 1,4-diazabicyclo[2.2.2]octane was used as a Lewis base in DMF, the aza-Baylis-Hillman reaction of 1 with MVK gave the double aza-Baylis-Hillman adduct 3 exclusively in moderate to good yields with excellent diastereoselectivities. The double Baylis-Hillman adduct 3 was conveniently converted to fluorine-containing 4-alkylidene-2-cyclohexen-1-ones under mild reaction conditions in good yields.     

Room temperature ionic liquids promoted three-component coupling reactions: a facile synthesis of cis-isoquinolonic acids

Room temperature ionic liquids are found to catalyze efficiently the three component-coupling reactions of aldehydes, amines and homophthalic anhydride under mild and convenient conditions to afford the corresponding cis-isoquinolonic acids in excellent yields with high cis-selectivity.     

Free energy landscapes of prototropic tautomerism in pyridoxal 5′‐phosphate schiff bases at the active site of an enzyme in aqueous medium

We have performed hybrid quantum‐classical metadynamics simulations and quantum chemical calculations to investigate the free energy landscapes of intramolecular proton transfer and associated tautomeric equilibrium in pyridoxal 5 ‐phosphate (PLP) Schiff Bases, namely the internal and external aldimines, at the active site of serine hydroxymethyltransferase (SHMT) enzyme in aqueous medium. It is important to determine the relative stability of the two tautomers (ketoenamine and enolimine) of the PLP aldimines to study the catalytic activity of the concerned enzyme. Both the internal PLP aldimine (PLP‐LYS) and the external PLP aldimine (PLP‐SER) of SHMT are found to have a higher stability for the ketoenamine tautomer over the enolimine form. The higher stability of the ketoenamine tautomer can be attributed to the more number of favorable interactions of the ketoenamine form with its surroundings at the active site of the enzyme. The ketoenamine is found to be stabilized by about 2.5 kcal/mol in the PLP‐LYS internal aldimine, while this stabilization is about 6.7 kcal/mol for the PLP‐SER external aldimine at the active site of the enzyme compared to the corresponding enolimine forms. The interactions faced by the PLP aldimines at the active site pocket determine the relative dominance of the tautomers and could possibly alter the tautomeric shift in different PLP dependent enzymes. © 2018 Wiley Periodicals, Inc.     

Elimination reactions of N,C-difluorides

Hydrogen fluoride was eliminated from N,C-difluorinated derivatives of bis(polynitroalkyl)amines by the action of alkanols. Previously unreported -fluoropolynitroalkylaldimines were obtained.Institute of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 742–743, March, 1992.     

Study of alkaloids of the Siberian and Altai flora. 7. Synthesis of 18-amino-18-deoxy derivatives of elatidine

Reduction of elatidal oxime and imines based on methylamine, ethanolamine, tyramine, and S- and (±)-alaninols gave rise to the 18-amino-18-deoxy derivatives of elatidine.     

Indium triflate-catalyzed allylation reactions of N-sulfonyl aldimines or N-alkoxycarbonylamino p-tolylsulfones with allyltrimethylsilane: synthesis of protected homoallylic amines

Indium triflate-catalyzed allylation reactions of N-sulfonyl aldimines or N-alkoxyloxycarbonylamino p-tolylsulfone with allyltrimethylsilane have been successfully developed to produce protected homoallylic amines.     

Zinc-Mediated Addition of Bromoacetonitrile to Aldimines

Thecarbon-nitrogendoubleb0ndhaselectrophilicityandtlleadditi0nofcarbonnucle0-plillestocarbon-nitf0gendoublebondinilninesconstitutesanimpohalltmeti1odforti1eprepamtionofsecondnyamines.Asaclleapai1defficientreagentmetalliczinchasbeenwidelyusedinil1eallylationofaldehydesandket0nes',aswellasilnines2.Itissh0wnll1atzinclinsalilghreactivitytomediatehleforlnation0fcarbon-carbonbondundermildreachoncondihons,anditwouldhaVeawiderusein0rganicSynti1esis.BecauseofitselectronwitlldrawiIlgproperty,llleCNgro…