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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.
Ketene cycloadditions proceed by a concerted, [2+2] cycloaddition mechanism. Ketenes, unlike most alkenes, can align antarafacially with respect to other alkenes. Thus, the suprafacial- antarafacial geometry required for concerted, thermal [2+2] cycloaddition can be achieved in reactions of ketenes. [4]
The reverse or retro-Cope elimination has been reported, in which an N,N-disubstituted hydroxylamine reacts with an alkene to form a tertiary N-oxide. [ 9 ] [ 10 ] The reaction is a form of hydroamination and can be extended to the use of unsubstituted hydroxylamine, in which case oximes are produced.
They will also undergo [2+2] cycloaddition reactions with electron-rich alkynes to form cyclobutenones, or carbonyl groups to form beta-lactones. With imines, beta-lactams are formed. This is the Staudinger synthesis, a facile route to this important class of compounds. With acetone, ketene reacts to give isopropenyl acetate. [1]
The Heck reaction is the palladium-catalyzed coupling of an aryl or alkenyl halide with an alkene to form a substituted alkene. [2] Intramolecular variants of the reaction may be used to generate cyclic products containing endo or exo double bonds.
Monosubstituted trans-2-Butene 116 27.6 Disubstituted 2-Methyl-2-butene 113 26.9 Trisubstituted 2,3-Dimethyl-2-butene ... In an alkene, the bond angle increases to ...
Methanesulfonamide (CH 3 SO 2 NH 2) has been identified as a catalyst to accelerate this step of the catalytic cycle and if frequently used as an additive to allow non-terminal alkene substrates to react efficiently at 0 °C. [8] Finally, the stoichiometric oxidant regenerates the osmium tetroxide – ligand complex (2).
In organic chemistry, alkylidene is a general term for divalent functional groups of the form R 2 C=, where each R is an alkane or hydrogen. [1] They can be considered the functional group corresponding to mono- or disubstituted divalent carbenes (known as alkylidenes), [2] or as the result of removing two hydrogen atoms from the same carbon atom in an alkane.