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Relevant academic research and scientific papers

Stereoselective Synthesis of Vinyl Iodides through Copper(I)-Catalyzed Finkelstein-Type Halide-Exchange Reaction

An efficient method for the stereoselective synthesis of vinyl iodides is described. The reactions of vinyl bromides with potassium iodide proceed smoothly in the presence of a copper catalyst under mild reaction conditions to produce the corresponding vinyl iodides stereospecifically and in satisfactory to excellent yields.

Stereoselective hydrogenolysis of 1,1-dibromo-1-alkenes and stereospecific synthesis of conjugated (Z)-alkenyl compounds

The Pd-catalyzed hydrogenolysis of 1,1-dibromoalkenes with Bu3SnH occurs at room temperature stereoselectively to give (Z)-1-bromo-1-alkenes. We sought to determine the optimal reaction conditions and illustrate the scope of this method with 32 dibromoalkenes including alkenyl- and alkynyl- conjugated 1,1-dibromo-1-alkenes 7a-h and 2,2-disubstituted 1,1-dibromo-1- alkenes 9af. Triphenylphosphine was the best ligand for the Pd-catalyzed hydrogenolysis. A wide range of solvents can be used for this reaction excluding EtOH, AcOH, and CHCl3. However, the reaction proceeds even in these solvents with the addition of a cosolvent or radical scavenger. The reaction of 1,1-diiodo-1-alkene (3) gave a mixture of (Z)-1-iodo-1-alkene (4), (Z)-1-tributylstannyl-1-alkene (5), and a terminal alkene 6, while that of 1,1-dichloroalkene did not occur. This selectivity can be explained by the stereoselective insertion of Pd(0) to a trans bromine-alkenyl carbon bond, successive transmetalation with Bu3SnH, and reductive elimination. The Suzuki and Sonogashira couplings of the resulting (Z)-1-bromo-1-alkenes with alkenyl(dialkoxy)borane and terminal alkyne occurred to give conjugated polyenes and enynes stereospecifically. The Pd-catalyzed hydrogenolysis of 1,1-dibromo-1-alkene and successive cross-coupling can be carried out either in a stepwise manner or in one-pot under the same Pd catalysis. These two processes should be useful for the synthesis of geometrically pure polyene and enyne with a Z-alkenyl unit.

A general and convenient synthetic method of geometrically pure (Z)-1-bromo-1-alkenes

Palladium catalyzed hydrogenolysis of 1,1-dibromo-1-alkenes by tributyltin hydride proceeds smoothly to give (Z)-1-bromo-1-alkenes with excellent stereoselectivity in good yields. Dibromomethylenation of aldehydes by a combination of CBr4 and P

Stereochemistry in carbenoid formation by bromine/lithium and bromine/zinc exchange reactions of gem-dibromo compounds

Stereochemistry in generation of lithium and zincate carbenoids by bromine/metal exchange reactions of gem-dibromo compounds with BuLi and lithium triorganozincates, respectively, has been investigated. Both lithium and zincate carbenoids derived from 1,1

Reactions of 1,1-Dihaloalkenes with Triorganozincates: A Novel Method for the Preparation of Alkenylzinc Species Associated with Carbon-Carbon Bond Formation

Lithium trialkylzincates react with 1,1-dibromoalkenes 1 and 1-bromo-1-chloroalkenes 2 at -85 deg C in THF to give 1-bromoalkenes 5 and 1-chloroalkenes 7, respectively, upon hydrolysis.The intermediate (1-haloalkenyl)zincates 4 and 6 are stable at low temperature but, when allowed to warm to 0 deg C, they undergo a 1,2-alkyl migration reaction to afford alkenylzinc species 10.A variety of alkylation products 11 are obtained by the hydrolysis of 10.In the presence of (Ph3P)2Pd (5 molpercent), alkenylzinc species 10 react smoothly with organic halides (AcCl, EtOCOCl, CH2=CH(Me)Br, PhBr) to yield the corresponding coupling products 13-16.

Stereochemistry in Carbenoid Formation by Bromine/Lithium and Bromine/Zinc Exchange Reactions of 1,1-Dibromoalkenes: Higher Reactivity of the Sterically More Hindered Bromine Atom

Both lithium and zincate carbenoids (R1(R2)C=C(Br)M; M = Li and Zn(Bu)2Li) generated by the halogen/metal exchange reaction of 1,1-dibromoalkene 1 with BuLi and (Bu)3ZnLi, respectively, are configurationally stable at low temperature

GENERATION AND ALKYLATION REACTION OF 1-BROMOALKENYLZINCATE

1-Bromoalkenylzincates (R1R2C=CBrZnR32Li) which are generated by the reaction of 1,1-dibromoalkenes with a lithium triorganozincate (R33ZnLi) at -85 deg C undergo alkylation reaction at temperatures from -85 deg C to 0 deg C to give alkenes R1R2C=CHR3.