Further Developments on the Regioselective Synthesis of 3-Aroylindole Derivatives from C-Nitrosoaromatics and Alkynones: A Novel Synthetic Approach to Pravadoline, JWH-073, Indothiazinone Analogues and Related Compounds

An uncatalyzed and easily accessible synthetic approach for the preparation of 3-aroylindoles was investigated using nitrosoarenes and aromatic terminal ethynyl ketones. Indole derivatives were produced in good yields and excellent regioselectivity. Functionalizations of the indole products were carried out affording highly valuable and versatile compounds. The indolization protocol was studied as a fundamental step for the preparation of pravadoline and 1-butyl-3-(1-naphthoyl)indole (JWH-073), bioactive molecules showing antinociceptic properties.

Nickel-catalyzed asymmetric arylative cyclization of N-alkynones:Efficient access to 1,2,3,6-tetrahydropyridines with a tertiary alcohol

Nickel/(S)-t-Bu-PHOX complex catalyzed asymmetric arylative cyclization of N-alkynones has been achieved, delivering 1,2,3,6-tetrahydropyridines containing a chiral tertiary alcohol in high yields and excellent enantioselectivities, which provides efficient access to chiral tetrahydropyridine and piperidine analogues.

Reactions of a 16-electron Cp*Co half-sandwich complex containing a chelating 1,2-dicarba-closo-dodecaborane-1,2-dithiolate ligand with alkynones HC≡C-C(O)R (R=OMe,Me,Ph)

The reaction of the 16e half-sandwich complex Cp*Co(S2C2B10H10) (1) (Cp* = pentamethylcyclopentadienyl) with excess methyl acetylene monocarboxylate, HC≡C-CO2Me, affords the 18e complexes 2-6. Compound 2 bears a B-CH2 unit in which B-substitution occurs in the B(3)/B(6) position of the ortho-carborane cage. Complexes 3-6 are geometrical isomers, in which the alkyne is twofold inserted into one of the Co-S bonds in all the four possible ways. Treatment of 1 with excess 3-butyn-2-one or phenyl ethynyl ketone, HC≡C-C(O)R (R = Me, Ph), at ambient temperature leads to the 18e complexes 7-10, respectively, with two alkynes inserted into one of the Co-S bonds. All the new complexes were fully characterized by spectroscopic techniques and elemental analysis. The solid-state structures of 2, 3, 5, 7, 8, 9 and 10 were further characterized by X-ray structural analysis.

A New Synthetic Method of Highly Substituted Cyclopentadienes from α,β-Unsaturated Alkynones

Promoted by samarium diiodide in THF, the α,β-unsaturated alkynones were reduced to afford intermolecular reductive coupling products. The multiply substituted cyclopentadienes were prepared conveniently in good yields.

Divergent synthesis of chiral amines via Ni-catalyzed chemo-and enantioselective hydrogenation of alkynone imines

Ligand-mediated nickel-catalyzed asymmetric hydrogenation of alkynone imines has been achieved. By using Ni(OAc)_2·4H_2O/(S,S)-Ph-BPE complex as a catalyst, the chemo-and enantioselective hydrogenation of alkynone imines occurred efficiently to afford chiral propargyl amines with high yields and excellent enantioselectivities(up to 99% yield, >99% ee), leaving the readily reducible alkynyl group intact. Both the C=N and C≡C bonds of alkynone imines were hydrogenated efficiently in the presence of Ni(OAc)_2·4H_2O and Josiphos SL-J011-1, furnishing unfunctionalized chiral imines efficiently(up to 99% yield, >99% ee).The(Z)-allylamines and(E)-allylamines were also efficiently prepared from alkynone imines by the combination of the different catalytic systems. The preliminary mechanism study revealed that the reduction of alkynone imines was a stepwise process and the C=N bonds were preferably hydrogenated in the complete reduction of alkynone imines. The synthetic utility of this method was demonstrated by its application in the late-stage modification of the antiviral drug Zidovudine and the concise synthesis of chiral dibenzoazepine.

Facile syntheses of 3-trifluoromethylthio substituted thioflavones and benzothiophenes via the radical cyclization

3-CF3 S substituted thioflavones and benzothiophenes were achieved via the reactions of AgSCF3 with methylthiolated alkynones and alkynylthioanisoles,respectively,promoted by persulfate.This protocol possesses good functional group tolerance and high yields.Mechanistic studies suggested that a classic two-step radical process was involved,which includes addition of CF3 S radical to triple bond and cyclization with SMe moiety.

Formation, Isolation and Characterization of a New Ruthenium Complex in Reaction of Acetone Masked Terminal Alkynone with Transfer Hydrogenation Catalyst

Reaction of [1S,2S-(Ts-diphen)Ru(II)(p-cymene)] (1S,2S-Ts-diphen=1S,2S-N-tosyl-1,2-diphenylethylenedi- amine) and 2-hydroxy-2-methyl-non-3-yn-5-one under transfer hydrogenation condition gave a ruthenium complex bearing a 2,5-dihydrofuran moiety. The complex was characterized and a possible mechanism for the formation of the complex was proposed.