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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.
[1] [2] It is also used in chemical synthesis as a precursor to carvone and as a renewables-based solvent in cleaning products. [1] The less common (-)-isomer has a piny, turpentine-like odor, and is found in the edible parts of such plants as caraway, dill, and bergamot orange plants. [3] Limonene takes its name from Italian limone ("lemon"). [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.
Monosubstituted trans-2-Butene 116 27.6 Disubstituted 2-Methyl-2-butene 113 26.9 Trisubstituted ... 109.5°. In an alkene, the bond angle increases to near 120°. ...
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.
Alkene substrates are often classified according to their substituents, e.g., 1,1-disubstituted, 1,2-diaryl trisubstituted, 1,1,2-trialkyl and tetrasubstituted olefins. [ 44 ] [ 45 ] and even within these classes variations may exist that make different solutions optimal.
There is a notable rate enhancement when certain Diels–Alder reactions are carried out in polar organic solvents such as dimethylformamide and ethylene glycol, [13] and even in water. [14] The reaction of cyclopentadiene and butenone for example is 700 times faster in water relative to 2,2,4-trimethylpentane as solvent. [14]
Hydrosilanes can reduce 1,1-disubstituted double bonds that form stable tertiary carbocations upon protonation. Trisubstituted double bonds may be reduced selectively in the presence of 1,2-disubstituted or monosubstituted alkenes. [15] Aromatic compounds may be reduced with TFA and triethylsilane.