Ray V.H. Jones

A zirconium catalysed synthesis of 1,4-dimagnesium reagents.

Abstract The zirconium catalysed addition of diethylmagnesium to a variety of unactivated alkenes affords either the simple carbometallation product, or, 1,4-dimagnesium reagents depending on the conditions and substrate. The products can be successfully functionalised with a variety of electrophiles.

The mechanism of the zirconium catalysed ethyl- and 2-magnesioethyl-magnesiation of unactivated alkenes

Abstract Deuterium labelling experiments prove that the zirconocene dichloride catalysed ethylmagnesiation of alkenes occurs via a zirconocene η2-ethylene complex and allow a deuterium isotope effect for a key β-hydride transfer to be estimated ( k H k D = 2.5 ). Transmetallation from zirconium to magnesium to form 1,4-dimagnesiated reagents is shown to be an intramolecular process. Kinetic studies show that the reaction between η2-ethylene zirconocene and the alkene is rate limiting and that Lewis bases inhibit the reaction by decreasing the amount of η2-ethylene zirconocene in equilibrium with the ‘ate’ complex [Cp2Zr(CH2=CH2)Et]−.[MgX.Base]+.

Catalytic asymmetric carbomagnesiation of unactivated alkenes. A new, effective, active, cheap and recoverable chiral zirconocene

Abstract The ethylmagnesiation of terminal alkenes catalysed by ( R , R )-ethylene-1,2-bis(η 5 -4,5,6,7-tetrahydro-1-indenyl)zirconium( R )-1,1′-binaphth-2,2′-diolate gave low turnovers and enantioexcesses. A novel C i symmetric zirconocene dichloride CpCp′ZrCl 2 (Cp = C 5 H 5 , Cp′ = 1-neomenthyl-4,5,6,7-tetrahydroindenyl) was prepared which gave better enantioselectivity, is cheaper to make, catalytically more active, and recoverable.

Rearrangements of phenylthio substituted 1,n-diols with toluene-p-sulfonic acid and with toluene-p-sulfonyl chloride

Abstract Rearrangement of a series of 1,n diols (n= 2 to 12), one OH group having an adjacent PhS group, under the two sets of conditions in the title, gives single compounds in high yield drawn from four possible classes of product. The effects of chain length help in our understanding of the mechanism of the rearrangements.

Crystal to molecular chirality transfer: Supramolecular photochemistry of crystalline carboxylate salts

Abstract Solid state irradiation of a salt formed between a prochiral, photochemically reactive carboxylic acid and a non-absorbing, optically active amine is shown to lead to an optically active Norrish type II photoproduct whose optical purity depends on the dimorphic crystalline modification photolyzed.

Zirconium-catalysed enantioselective 2-aluminoethylalumination of alkenes

Abstract Asymmetric 2-aluminoethylalumination of mono-substituted alkenes and 2,5-dihydrofurans catalysed by (R,R)-ethylene-1,2-bis(η5-4,5,6,7-tetrahydro-1-indenyl)zirconium (R)-1,1′-binaphth-2,2′-diolate 4 and η5-cyclopentadienyl-η5-(1-neomenthyl-4,5,6,7-tetrahydroindenyl)zirconium dichloride 5. gave 30 – 99% enantiomeric excesses. The so formed organoaluminium has potential for further elaboration leading to enantiomerically enriched products.

The use of chiral sulfides in catalytic asymmetric epoxidation

Abstract Non racemic epoxides with ees of 23–41 % have been prepared from aldehydes and phenyl diazomethane using catalytic amounts of sulfides derived from camphor.

A NOVEL CATALYTIC CYCLE FOR THE SYNTHESIS OF EPOXIDES USING SULFUR YLIDES : APPLICATION TO BASE SENSITIVE ALDEHYDES

Abstract Epoxidation of base sensitive aldehydes can be achieved by a new catalytic cycle which requires the slow addition of a diazocompound to a solution of an aldehyde containing catalytic quantities of a sulfide and catalytic quantities of rhodium acetate.

ASYMMETRIC ETHYLMAGNESIATION OF ALKENES USING A NOVEL ZIRCONIUM CATALYST

Abstract The novel C 1 -symmetric zirconocene CpCp ∗ ZrCl 2 (Cp=C 5 H 5 , Cp ∗ = 1-neomenthyl-4, 5, 6, 7-tetrahydroindenyl ) is a cheap, active, and effective catalyst for the asymmetric ethylmagnesiation of unactivated terminal alkenes.

A novel procedure for the synthesis of aziridines: application of Simmons–Smith reagents to aziridination

The reaction of Simmons–Smith carbenoids with imines in the presence of sulfides provides N-(p-toluenesulfonyl)- and N-[(1,1,1-trimethylsilyl)ethyl]sulfonyl-substituted aziridines in high yield.