Synthesis of novel cyclohexanediol-derived chiral phosphite ligands and their application in the Cu-catalyzed conjugate addition of organozinc to cyclic enones

A series of novel chiral diphosphite ligands have been synthesized from（1R,2R）-trans-1,2-cyclohexanediol,（1S,2S）-trans-1,2-cyclohexanediol, racemic trans-1,2-cyclohexanediol and chlorophosphoric acid diary ester, and were successfully employed in the Cu-catalyzed asymmetric 1,4-conjugate addition of diethylzinc to cyclohexenone with up to 99% ee. It was found that ligand 1,2-bis[（R）-1,10-binaphthyl-2,2＇-diyl]phosphitecyclohexanediol 6a derived from racemic diol skeleton can show similar catalytic performance compared with ligand（1R,2R）-bis[（R）-1,1＇-binaphthyl-2,2＇-diyl]phosphitecyclohexanediol 6a＇ derived from enantiopure starting material. A significant dependence of stereoselectivity on the type of enone and the ring size of the cyclic enone was observed. Moreover, the configuration of the products was mainly determined by the configuration of the binaphthyl moieties of diphosphite ligands in the 1,4-addition of cyclic enones.

Synthesis of Novel Tartaric Acid-derived Chiral Phosphite Ligands and Their Application in the Cu-catalyzed Conjugate Addition of Diethylzinc to Cyclic Enones

Five novel tropos （3R,4R）- and/or （3S,4S）-N-benzyltartarimide-derived biphenylphosphite ligands were synthesized and applied in the Cu-catalyzed asymmetric conjugate addition of diethylzinc to cyclic enones with up to 75% e.e. Compared with the reported ligand 1-N-benzylpyrrolidine-3,4-bis[（R）-1,1＇-binaphthyl-2,2＇-diyl]phosphite- L-tartaric acid, the issue that L-（＋）-tartaric acid backbone and （R）-binaphthyl showed strong matched/mismatched character was solved with these tropos ligands. It was found that the enantioselectivity was mainly controlled by the absolute configuration of N-benzyltartarimide backbone, and both enantiomers of the addition products can be obtained by simply changing the configuration of N-benzyltartarimide substituent.

Enantioselective Hydrogenation of Endocyclic Enones:the Solution to a Historical Problem

Main observation and conclusion The enantioselective hydrogenation of endocyclic enones has been a historical problem for homogeneous catalysis.We herein report an efficient method to reduce endocyclic enones with molecular hydrogen.Catalyzed by a rhodium/Zhaophos complex,a variety of enones with five-,six-or seven-member ring were hydrogenated with high enantioselectivity(92%-99%ee).Excellent chemo-and enantioselectivity demonstrated this method was successfully applied in the enantioselective hydrogenation of citral to produce enantio-enriched citronellal.

An unexpected Diels-Alder type cycloaddition of cyclic enone ethylene ketals

The ethylene ketal of 2-cyelopentenone and 2-cyelohexenone in acetonitrile in the presence of a trace of an acid rapidly undergoes the Diels-Alder type dimerization,The products are regiospecific but not stereoselective and are hydrolysed sequentially to afford keto-ketals and diketones whose structures are determined by extensive applications of NMR spectroscopy.

Transition metal-free dearomatization of halonaphthols with C(sp^(3))-electrophiles

The first intermolecular electrophilic dearomatization of halonaphthols with benzyl/allyl bromides is described. Halonaphthols are used as carbon-nucleophiles in dearomatization to form three-dimensional cyclic enones with excellent chemoselectivity, in which etherification of phenolic hydroxyl group could be restrained well by using cesium carbonate as the base. A wide range of cyclic enones is directly prepared from various substituted benzyl/allyl bromides and halonaphthols. Mechanistic investigations suggest a direct S_(N)2 reaction pathway.