36678-05-4

Rhodium-catalyzed hydroformylation of vinyl acetate with the use of diphosphine ligands was studied. A high regioselectivity (branched:linear of 99:1) and activity (TOF: 4000 h-1) under optimum conditions were achieved by using a 2,2'-bis(diphenylphosphino methyl)-1,1'-biphenyl ligand. The high turnover number (9200) obtained under mild conditions and stability of the catalyst indicates that it would be useful for industrial vinyl acetate hydroformylation.

-

Glycol monoesters were produced by oxidation of acetals with oxygen, hydroperoxides, hydrogen peroxide, hydrotrioxide and ozon.Addition of salts of metals of variable valency and crown-ether substantially increase the rate of oxidation and hydroxylation.The most efficient oxidizer is ozon.

-

Diols and their formic or acetic esters can be carbonylated to give lactones or the corresponding hydroxyacid ester or ethers in the presence of carbonylruthenium iodide systems. -/alkyl or metal iodide, at a temperature of 200 deg C and CO pressure of 10-20 MPa.The reaction in the case of 1,3-propanediol gives γ-butyrolactone, with a selectivity of 60-70 percent.Side reactions of homologation to 1,4-butanediol derivatives and hydrogenolysis to n-propyl derivatives by H2 produced by the water gas shift reaction (WGSR) also occur, together with acid-catalyzed dehydration to give linear polypropylene glycols, α,ω-diols with more than 3 carbon atoms in the chain preferentially give hydroxyacid esters and ethers.The cyclic ether by-products and linear polyether by-products can be further activated and carbonylated under the reaction conditions to give lactones or hydroxy-acid derivatives thus increasing the total yield of carbonylation products.The formation of H2 by WGSR involving water produced by the acid-catalyzed dehydration reactions, and the subsequent hydrogenolysis and homologation reactions cannot be avoided.

The oxidation of terminal olefins by bis(acetonitrile)chloronitropalladium(II) (1) in acetic acid leads to a mixture of glycol monoacetate isomers as the main products.Various amounts of ketones and unsaturated acetates are also formed.The rate of formation and the yield of glycol monoacetate decrease with increasing chain length.Cyclic olefins yield no glycol monoacetates.Replacement of acetic acid by stronger or sterically hindered carboxylic acids completely eliminates the formation of glycol monocarboxylates.Introduction of oxygen converts this stoichiometric reaction into a catalytic system.Our studies, including those carried out with complex 1 labeled with 18O in the nitro ligand, suggest that the glycol monoacetates and most of the ketones are the product of oxygen atom transfer from the nitro group, while the unsaturated acetates are the result of a Wacker-type reaction.In the glycol monoacetate, the 18O label is found exclusively in the acetate group.A mechanism which is in agreement with the above observations as well as a comparison of the above reaction with the oxidation of olefins by nitrate ions in the presence of palladium(II) salts is offered.The formation of glycol monoacetates in the monometallic system represented by complex 1 is to be compared with the results obtained in the bimetallic systems consisting of a combination of py(TPP)CoNO2 and either (CH3CN)2PdCl2 or Pd(OAc)2.In the latter systems, ketones or vinyl acetates are found as the predominant products.This fact underlines the difference between the mono- and bimetallic systems and strongly argues against alternative mechanisms involving nitro group transfer from cobalt to palladium before the olefin oxidation takes place.Additional evidence underlining the difference between these two systems is presented.

The hydroboration of alkenes containing representative functional groups was examined with 9-borabicyclononane (9-BBN) in order to extend the hydroboration reaction for the preparation of functionally substituted organoboranes.Terminal alkenes containing a remote functional group are hydroborated with a remarkable regioselectivity (>=98percent terminal), producing the corresponding stable organoboranes. 9-BBN hydroborates the allylic derivatives so as to place boron essentially on the terminal carbon atom (>=97percent).The directive effect is further enhanced (>=99percent) in the case of β-methylallyl derivatives.The hydroboration of crotyl derivatives attaches boron predominantly at the 2-position, followed by an elimination-rehydroboration sequence.However, crotyl alcohol can be protected against elimination as the tert-butyl or tetrahydropyranyl ethers.The hydroboration-oxidation of ethyl crotonate involves a series of elimination, hydroboration, and condensation processes.In the vinyl, crotyl, and isobutenyl systems, the mesomeric effect of the substituent favors the placement of boron at the β-position, while the inductive effect favors the α-position, with the former effect predominating in most cases.Acyclic β-substituted organoboranes undergo rapid elimination.Nonpolar solvents and lower reaction temperatures decrease the rate of elimination.However, those derived from cyclic vinyl derivatives are relatively stable under neutral conditions, undergoing facile elimination in the presence of a base.