Search

Synthesis and use of Pulegone-derived bidentate P,S ligands PuPHOS and CyPuPHOS in the intermolecular Pauson-Khand reaction (PKR) were described. Intermolecular PKR of trimethylsilylacetylene complex occurred in a completely stereospecific fashion to yield optically enriched cyclopentenone.

Research has been conducted on the enantiopure 10-(R-thio)-2-exo-bornanethiols. The procedure for the preparation of these compounds from (1S)-camphor-10-thiol has been developed and the results demonstrate that the ethynyl derivatives of these thiols produce excellent diastereoselectivities in Pauson-Khand reactions with norbornene and norbornadiene.

A synthetically useful catalytic process for the reduction of five- and six-membered lactones using polymethylhydrosiloxane as the stoichiometric reductant was designed. Two strategies were developed such that straightforward activation of the precatalyst produces an efficient catalyst for the hydrosilylation of lactones. A simple aqueous workup frees the lactol products, which can be purified and isolated in good to excellent yields.

A simple and convenient methodology for the preparation of optically pure 2-amino-2-aryl-1,1-diphenylethanols is presented. Removal of allyl protecting group provided the free 1,2-amino alcohols in enantiomerically pure form.

A myriad of tricyclo[5.2.1.0]deca-4,8-dien-3-ones is prepared by using norbornadiene as alkene. The interpretation of the experiments is that the photorearrangement has taken place through [super 3]([pi][pi]*) state as the energy barrier involved in the initial C-C [gamma]-bond cleavage of the enone is much lower in the [super 3]([pi][pi]*) potential energy surface (PES) than in the [super 1](n[pi]*) PES.

The synthesis of a family of racemic and optically pure N-phosphino-p-tolylsulfinamide (PNSO) ligands and their stability and coordination behavior toward dicobalt-alkyne complexes are reported. The results provide insight into the presence of an aryl group on the sulfinamide that reduces the hemilabile character of the PNSO ligands.

A unique methine moiety attached to three heteraoatoms (O,P,S) and contained in the PuPHOS and CamPHOS ligands serves as a strong hydrogen-bond donor. The hydrogen-bond bias obtained in the ligand exchange process is exploited in the asymmetric intermolecular Pauson-Khand reaction to yield the corresponding cyclization adducts.

The introduction of 2-piperidino-1,1,2-triphenylethanol as a catalyst, has led to the ligand-catalyzed arylation of aldehydes. The kinetic, experimental and theoretical reports describe the different aspects involved in the most synthetically useful phenylation reaction.

A family of camphor-derived chiral auxiliaries were successfully used in Pauson-Khand chemistry. Theoretical calculations were used to analyze the origin of the diastereoselectivity seen when using the new chelating auxiliaries. The dicobalt hexacarbonyl complexes of the alkoxyacetylenes derived, were converted into stable pentacarbonyl complex. The Pauson-Khand reactions with strained olefins occurs with synthetically useful rates at low temperatures.

The Pauson-Khand reaction is discussed in the context of a new chiral bidentate ligand.

Lactones can be converted into cyclic ethers through a two-step procedure with excellent yields. The procedure starts with the reduction of lactone to lactol through a reduction procedure utilizing a titanocene complex and a reducing agent. Triethylsilane and Amberlyst 15 can then be applied to the crude product to generate the cyclic ether.

The first highly enantioselective technique for the catalytic hydrosilylation of imines is presented. This experimentally simple process involves a unique activation process based on the reaction of (S,S)-ethylenebis(eta5-tetrahydroindenyl)titanium difluoride with phenylsilane. The process transforms imines to amines under mild conditions with substantially higher substrate:catalyst ratios than previously possible.

The five- and six-membered ring lactones are reduced to lactols in the presence of an active catalyst, titanocene(III) hydride. The conversion of lactones to lactols proceeds at room temperature and pressure and uses air-stable reducing agent, polymethylhydrosiloxane. The lactone adds to the titanium-hydrogen bond to give the titanium alkoxide which undergoes sigma-bond metathesis with silane to form the silylated lactol and titanium hydride.

Pauson-Khand reaction can be chirally controlled and used for the synthesis of enantioselective cyclopentenone. Studies using norborene exhibit change in diastereoselectivity, with temperature indicating the participation of a common intermediate that is reactive toward olefin coordination. Auxiliary 10-methyl thio-isoborneol acts as an effective chiral controlled for Pauson-Khand reactions.