Search

Research has been conducted on Nicholas reaction on solid phase. Results demonstrate that this reactions involves the reaction of cobalt complexes of polymer-bound alkynols with various nucleophiles in the presence of Lewis acid.

Research was conducted to examine the synthesis of P-N-P bidentate ligands, assess their pi-acceptor properties in the complexes obtained from phenylacetylene-dicobalt hexacarbonyl and to describe the reactivity of the complexes in the Pauson-Khand reaction. Experimental results show that the important bond distances and angles in the ligands agree with literature values. Findings may help in the design of effective chiral ligands for a new approach to asymmetric Pauson-Khan reactions.

A novel procedure for the high-yield synthesis of S-alkyl and S-aryl ynethiol ethers is described. The one-pot procedure follows the sequence thiol-thiolate-dichloro-enethiol ether-ynethiol ether. Excellent results have been obtained with primary, secondary and tertiary thiols and with thiophenols. The reaction conditions for each synthesis are presented.

Investigations pertaining to the interactions between meso dialdehydes and chiral Horner-Wadsworth-Emmons reagents elucidate the usefulness of meso dialdehydes as substrates for interactions with chiral phosphonate reagents. The synthetic properties of asymmetric alkene synthesis is enhanced as a result of meso dialdehyde-chiral phosphonate interactions, termed as asymmetric Horner-Wadsworth-Emmons reactions. These reactions yield monoaddition products of desired diastereospecificities and high (E)-selectivity.

The enantio-enriched form of [alpha]-formyl phosphine boranes were prepared via asymmetric deprotonation of prochiral phosphine boranes or by deprotonation of PAMP.B[H.sub.3] (o-anisyl methyl phenyl phosphine). The method provides insight into a new type of P-chirogenic compounds that are highly versatile building blocks for the design and construction of new chiral phosphine ligands.

An intermolecular asymmetric Pauson-Khand reaction can be used for the total synthesis of natural brefeldin A, a fungal metabolite. The cyclopentanone obtained as an intermediate in the Pauson-Khand reaction undergoes trans ketene acetal addition in the presence of a lithium perchlorate catalyst to form a precursor of (+)-brefeldin A.

Asymmetric Horner-Wadsworth-Emmons reactions between chiral phosphonate reagents and meso-dialdehydes were investigated. Experimental results showed that appropriate choice of chiral reagent and reaction conditions results in (E)- and (Z)-monoaddition products with good to excellent diastereoselectivities and in synthetically useful yields. Both the geometric selectivities and the levels of asymmetric induction were influenced by the structure of the phosphonate and, to a certain degree, by the reaction conditions.