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Alternative Mechanism. The Corey-Winter olefination is a stereospecific reaction: [1] a trans-diol gives a trans-alkene, while a cis-diol gives a cis-alkene as the product. For instance, cis- and trans-1,2-cyclodecanediol gives the respective cis- and trans-cyclodecene.
Thus, cyclohexene, diiodomethane, and a zinc-copper couple (as iodomethylzinc iodide, ICH 2 ZnI) yield norcarane (bicyclo[4.1.0]heptane). [5] [6]The Simmons–Smith reaction is generally preferred over other methods of cyclopropanation, [7] however it can be expensive due to the high cost of diiodomethane.
Hydroboration of 1,2-disubstituted alkenes, such as a cis or trans olefin, produces generally a mixture of the two organoboranes of comparable amounts, even if the steric properties of the substituents are very different. For such 1,2-disubstituted olefins, regioselectivity can be observed only when one of the two substituents is a phenyl ring.
These have been developed extensively, second only to the classical methylene reagents (R 1 =R 2 =H). The substitution pattern on aryl reagents can heavily influence the selectivity of the reaction as per the criteria above. If the ylide carbon is substituted with an alkyl group the reagent is referred to as an unstabilized ylide. The size of ...
Thus 1-methylcyclopentene reacts with diborane predominantly to give trans-1-hydroxy-2-methylcyclopentane [4] —the newly added H and OH are cis to each other. Until all hydrogens attached to boron have been transferred away, the boron group BH 2 will continue adding to more alkenes. This means that one mole of hydroborane will undergo the ...
1,2-Dibromoethylene, also known as 1,2-dibromoethene and acetylene dibromide, is a dihalogenated unsaturated compound with one bromine on each of the two carbon atoms. There are two isomers of this compound, cis and trans .
[1] [2] Grubbs catalysts tolerate many functional groups in the alkene substrates, are air-tolerant, and are compatible with a wide range of solvents. [ 3 ] [ 4 ] For these reasons, Grubbs catalysts have become popular in synthetic organic chemistry . [ 5 ]
m 1 –r + m 2 –x → m 1 –x + m 2 –r. In redox-transmetalation/ligand exchange the ligands of two metal complexes switch places with each other, bonding with the other metal center. The R ligand can be an alkyl, aryl, alkynyl, or allyl group and the X ligand can be a halogen, pseudo-halogen, alkyl, or aryl group.