Ibrahim Amer

Phosphine oxides as ligands in the hydroformylation reaction

Abstract A new rhodium-phosphine oxide system has been investigated in the hydroformylation reaction. Some of the phosphine oxide ligands of type 2–12 (i.e. R 2 N(CH 2 ) n P(O)R ′ 2 , R ′ = Ph , Cy ; n = 0, 2, 3,; R = Me, Et, i Pr , or NR2 = 2-pyridyl) were found to be better ligands than the phosphine analogues (i.e. R2N(CH)2PR′2) in the hydroformylation of olefins catalyzed by rhodium complexes. Detailed examination of factors controlling the selectivity for aldehydes formation revealed the following characteristics of the reaction: (a) use of ligands having bulkier amino groups decrease the yield of the aldehydes slightly; (b) ligands having amino groups with low basicity decrease the rate of the hydroformylation dramatically; (c) the electronic properties of the phosphine oxide group have no influence on the hydroformylation reaction; (d) uncoordinating solvents of low polarity such as dichloromethane, chloroform and toluene gave the best reaction rate and selectivity; (e) spectroscopic investigation of the hydroformylation of styrene catalyzed by rhodium with ligand 2 shows that the ligand is coordinated by the amino and the phosphine oxide groups under 1 atm of COue5f8H2 and only by the amino group under 600 lbf in−2 of COue5f8H2.

CERIUM-CATALYZED SELECTIVE OXIDATION OF ALKYLBENZENES WITH BROMATE SALTS

Abstract Cerium(IV) ammonium nitrate (CAN)-catalyzed oxidation of alkyl aromatics with potassium bromate affords aldehydes, ketones acids or alcohols in high yields.

Influence of (PN) bidentate ligand on rhodium-catalyzed hydroformylation of olefins

Abstract Mixed (Pue5f8N) bidentate ligands enhance the rhodium-catalyzed hydroformylation of olefins, and in the hydroformylation of styrene, provides good selectivity.

Cyclo-oligomerization and rearrangement of some phenylated diynes by the RhCl3Aliquat 336 and by the H2PtCl6Aliquat 336 catalysts under phase transfer conditions

Abstract The phenylated diynes 3,3′-oxybis(1-phenyl-1-propyne) ( 3 ), its thio-analog 4 , 1,2-bis(phenylethynyl)benzene ( 5 ) and 1,8-bis(phenylethynyl)naphthalene ( 6 ) were reacted, under phase transfer conditions, in the presence of the ion pairs generated from Aliquat® 336 and either aqueous RhCl 3 or H 2 PtCl 6 . The nature of the products proved to depend on the catalyst employed. The rhodium catalyst promotes the conversion of 3 into a mixture of trimer 8 and dimer 7a , as well as the hydrolysis of the latter compound to give 1,3-dihydro-4,6,7-triphenyl-5-isobenzofuranmethanol ( 9 ). The sulfur compound 4 yields only hydrolysis-resistant 1,3-dihydro-5-[2-propynyl(thiomethyl)]benzo[ c ]thiophen ( 7b ), and 6 forms mainly dimer 17 accompanied by small amounts of 7-phenyl- and 7-chloro-12-phenylbenzo[ k ]fluoranthene ( 16a and 16b , respectively). The platinum catalyst promotes particularly intramolecular cycloaddition reaction of the diynes. Compound 3 is transformed almost entirely to 1,3-dihydro-9-phenylindeno[1,2- c ]pyran ( 12 ), 5 is isomerized to give solely 5-phenylindeno[1,2- a ]indene ( 15 ), and 6 yields 16a and 12-phenylindino[2,1- a ]phenalene ( 18 ), as the minor and major products.

A convenient route to 1,3,5-trisubstituted benzenes via rhodium catalyzed polymerization of arylacetylenes

Abstract [(1,2,5,6-η)-1,5-Cyclooctadiene] (1,3-propanediamine-N,N′)rhodium(1+) chloride, [(COD)RhCl(H2NCH2CH2CH2NH2)]Cl, 11, and the water soluble complexes (COD)RhCl(Ph2PC6H4-3-SO3Na) 10, trans-[Rh(CO) (Ph2PC6H4-3-CO2H) (μ- NCMeue5fbCHCMeue5fbN )]2 12, (Ph2PC6H4-2-CO-O)-Rh(CO) ( NHMeue5fbCHCMeue5fbN ) 13a, (Ph2PC6H4-2-CO-O)-Rh(CO) (indazole) 13b and trans-[Rh(CO) (Ph2PC6H4-2-CHO) (μ- NCMeue5fbCHCMeue5fbN )]2 14 were shown to catalyze the polymerization of PhCue5fcCH 1 and the substituted arylacetylenes 2–8 at 25°C in a stereoregular manner. The cis-oriented poly(arylacetylenes), so formed, were found to depolymerize selectively at 200–225°C to the corresponding 1,3,5-triarylbenzene derivatives.

Selective cerium-catalyzed oxidation of alkyl benzenes to benzyl esters by bromate salts

Abstract Benzyl esters are formed catalytically at moderate temperatures from alkyl benzenes by KBrO 3 in the presence of cerium ammonium nitrate (CAN). Toluene gives in acetic acid benzyl acetate. Ethylbenzene, cumene, 4- tert -butyltoluene, and 4-bromotoluene give similar oxidation products. p -xylene undergoes a selective mono-acetoxylation reaction in acetic acid. The bromate salt is acting as an oxidant for the alkylbenzene and a cooxidant for the Ce salt. The Ce salts (Ce(III), Ce(IV)) serve both as oxidation catalysts and as Lewis acids that catalyze the conversion of benzyl bromide in the reaction mixture to benzyl ester.

Synthesis of α-methylene-β-lactones by nickel-catalyzed hydrocarboxylation of propargyl alcohols

Abstract Substituted α-methylene-β-lactones ( 2 ) were prepared in two steps, from substituted propargyl alcohols, by hydrocarboxylation under atmospheric pressure of CO in the presence of nickel cyanide under phase-transfer conditions. The α-methylene-3-hydroxypropanoic acid derivatives so formed (12–40% yield), were cyclized with mesyl chloride (22–56% yield).

Preparation and X-ray structure of a rhodium(III)-(S)- 6,6′-dimethyl-2,2′-diamino-biphenyl complex

Abstract trans-Dichlorobis[(S)-6,6′-dimethyl-2,2′-diaminobiphenyl]rhodium(III) chloride was prepared, and its structure was determined by X-ray diffraction.

Cobalt chloride and phase-transfer catalyzed carbonylation of benzyl chlorides

Abstract A cobalt chloride-potassium cyanide system was found to catalyze carbonylation of benzyl chlorides into arylacetic acids under phase-transfer conditions. The reaction takes place under mild conditions of temperature and carbon monoxide pressure. A catalytic cycle which includes complexes of the form Co(CN) 3- n ,(CO) n −2 2+ n ( n =0–2) as active species is proposed.

Phosphine vs. phosphine oxide ligands in hydroformylation reactions

In the hydroformylation of styrene catalysed by rhodium complexes, mixed amino phosphine oxide ligands show high reactivity and selectivity for the formation of the branched aldehyde.