Peter L. Pauson

The effect of ultrasound and of phosphine and phosphine-oxides on the Khand reaction

Abstract Ultrasonic irradiation allows the Khand reaction to be conducted rapidly at low temperatures. Addition of phosphine oxides to the reaction mixture significantly increases yields in most cases.

Tricarbonyl(phenylacetylene)chromium and tricarbonyl(styrene)chromium

Abstract The preparation and several reactions of tricarbonyl(phenylacetylene)chromium and tricarbonyl(styrene)chromium are described.

Optisch aktive Übergangsmetall-Komplexe: XCX. Optisch reines 3a,4,5,6,7,7a-Hexahydro-2-phenyl-4,7-methano-1H-inden-1-on durch asymmetrische Khand-Reaktion

Abstract The prochiral complex Co2(CO)6(HC2Ph) (I) obtained from the reaction of Co2(CO)8 with phenylacetylene, after reaction with the optical active phosphane Glyphos (II) gives the complex Co2(CO)5(HC2Ph)(Glyphos) which consists of two diastereomers (IIIa and IIIb) differing only in the chirality of the Co2C2 cluster. IIIa and IIIb can be separated by preparative liquid chromatography. They epimerize at higher temperatures, with the half life of the approach to the equilibrium IIIa/IIIb = 60 40 , at 60°C in toluene, being approximately 170 min. IN the Khand reaction of III with norbornene (IV) the cyclopentenone 3a,4,5,6,7,7a-hexahydro-2-phenyl-4,7-methano-1H-inden-1-one (V) is formed. The optical purity of V can be determined with the optishift reagent Pr(tfc)3. The equilibrium mixture IIIa/IIIb = 60 40 gives the (−)-cyclopentenone V in an enantiomeric purity of 36% ee. The optically pure (−)589-diasstereomer IIIb yields the enantiomerically pure (+)-cyclopentenone V, provided the epimerization is slow under the reaction conditions used.

Organocobalt complexes. Part II. Reaction of acetylenehexacarbonyldicobalt complexes, (R1C2R2)Co2(CO)6, with norbornene and its derivatives

Tetra- and hexa-hydro-4,7-methanoinden-1-ones and the analogous indacenediones (VIII)–(X) are formed stoicheiometrically by the title reaction or catalytically from acetylenes, norbornene derivatives, and carbon monoxide in the presence of octacarbonyldicobalt. The process leads stereoselectively to ketones of theexo-series and methyl or phenyl groups derived from the appropriate monosubstituted acetylenes are always found adjacent to the carbonyl group. The 1H n.m.r. spectra of the products are discussed and the use of an europium shift reagent together with spin decoupling is shown to allow clear distinction of the isomeric methanoindacenediones (VIII) and (IX).

Nucleophilic addition to transition metal complexes

Abstract The authors studies of nucleophilic addition, chiefly to cationic complexes of the hydrocarbon metal and hydrocarbon metal carbonyl types are reviewed and related to other work in the area. Effects studied include stereospecificity, regioselectivity, competition with substitution, and rearrangements.

Metal complexes of heterocycles II. N-pyrrolyl complexes of iron

Abstract Dicarbonylcyclopentadienyliron complexes σ-bonded through nitrogen to pyrrolyl-, 2-acetylpyrrolyl-, indolyl-, 1,2,3,4-tetrahydrocarbazolyl- and carbazolyl-groups are described.

Metal derivatives of conjugated dienes : II. Triphenylphosphine derivatives

Abstract The tricarbonyliron complexes of butadiene, cyclohexadiene, cycloheptadiene, cycloheptatriene and tetraphenylcyclobutadiene have been irradiated in the presence of triphenylphosphine. This ligand can replace one carbonyl group in all cases and a second one in the first three. The products in the cyclohexa- and heptadiene cases have been converted to the corresponding dienyliron fluoroborates with trityl fluoroborate. Addition of the latter reagent to the cycloheptatriene and of hydrogen chloride to the monophosphinebutadiene and cycloheptadiene complexes is also described. Tricarbonylcycloheptadienyliron tetrafluoroborate is converted by tertiary amines to tricarbonylcycloheptatriene-iron, but dimethylamine adds to give tricarbonyl-[5-(dimethylamino)cycloheptadiene]iron.

Metal complexes of heterocycles III. Aceẗylpyrrolyl and indolyl complexes

Abstract Tricarbonylmanganese complexes of 3-acetyl-2-methylpyrrole, 3-acetyl-2,4-dimethylpyrrole, 2-methylindole and tetrahydrocarbazole and (3-acetyl-2,4-dimethylpyrrolyl)cyclopentadienyliron are described. The NMR spectra of these and other π-pyrrolyl complexes are discussed.

Organocobalt complexes : VII. The role of butenolide complexes in the cobalt-catalysed synthesis of bifurandiones from acetylenes and carbon monoxide☆

Abstract The butenolide cobalt complexes derived from monosubstituted acetylenes are shown to be substituted in the α-position of the lactone ring. Their intermediacy in the catalytic formation of 2,6-disubstituted bifurandiones is demonstrated, and shown to require addition of both free acetylene and carbon monoxide.

The Khand reaction of some trisubstituted alkenes. Uses of the catalytic version of the reaction

Abstract Results are presented which suggest that in the absence of strong polar influences, 4,4,5-substituted cyclopentenones predominate over their 4,5,5-isomers when trisubstituted alkenes are employed in the Khand reaction. Double bonds shifts prior to annellation are a feature of two of the examples studied. Efficient use of these relatively unreactive alkenes is made possible by employing an acetylene/carbon monoxide atmosphere to allow recycling of the cobalt carbonyl fragment.