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When catalyzed by palladium carboxylates, a key step is
organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...
, hydrovinylation is the formal insertion
Insertion may refer to:
*Insertion (anatomy), the point of a tendon or ligament onto the skeleton or other part of the body
*Insertion (genetics), the addition of DNA into a genetic sequence
*Insertion, several meanings in medicine, see ICD-10-PCS
...
of an alkene
In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins.
The Internationa ...
into the C-H bond of ethylene
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...
():
:
The more general reaction, hydroalkenylation, is the formal insertion of an alkene into the C-H bond of any terminal alkene
In organic chemistry, terminal alkenes (alpha-olefins, α-olefins, or 1-alkenes) are a family of organic compounds which are alkenes (also known as olefins) with a chemical formula , distinguished by having a double bond at the primary, alpha ( ...
. The reaction is catalyzed by metal complex
A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or ...
es. A representative reaction is the conversion of styrene
Styrene is an organic compound with the chemical formula C6H5CH=CH2. Its structure consists of a vinyl group as substituent on benzene. Styrene is a colorless, oily liquid, although aged samples can appear yellowish. The compound evaporates easi ...
and ethylene to 3-phenybutene:
:
Ethylene dimerization
Thedimerization
In chemistry, dimerization is the process of joining two identical or similar molecular entities by bonds. The resulting bonds can be either strong or weak. Many symmetrical chemical species are described as dimers, even when the monomer is u ...
of ethylene which gives 1-butene
1-Butene (IUPAC name: But-1-ene, also known as 1-butylene) is the organic compound with the formula CH3CH2CH=CH2. It is a colorless gas, but easily condensed to give a colorless liquid. It is classified as a linear alpha-olefin (terminal alkene). ...
is another example of a hydrovinylation. In the Dimersol and Alphabutol Processes, alkenes are dimerized for the production of gasoline and for comonomers such as 1-butene. These processes operate at several refineries across the world at the scales of about 400,000 tons/year (2006 report). 1-Butene is amenable to isomerization to 2-butenes, which is used in olefin conversion technology Olefin Conversion Technology, also called the Phillips Triolefin Process, is the industrial process that interconverts propylene with ethylene and 2-butenes. The process is also called the ethylene to propylene (ETP) process. In ETP, ethylene is d ...
to give propylene
Propylene, also known as propene, is an unsaturated organic compound with the chemical formula . It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petroleum-like o ...
.
In organic synthesis
The addition can be done highly regio- and stereoselectively, although the choices of metal, ligands, and counterions often play very important role. Many metals have also been demonstrated to form active catalysts, including nickel and cobalt. In a stoichiometric version of a hydrovinylation reaction, nucleophiles add to an electrophilictransition metal alkene complex
In organometallic chemistry, a transition metal alkene complex is a coordination compound containing one or more alkene ligands. The inventory is large.Elschenbroich, C. "Organometallics" (2006) Wiley-VCH: Weinheim. Such compounds are intermediate ...
, forming a C-C bond. The resulting metal alkyl undergoes beta-hydride elimination, liberating the vinylated product.
Hydroarylation
Hydroarylation is again a special case of hydrovinylation. Hydroarylation has been demonstrated for alkyne and alkene substrates. An early example was provided by theMurai reaction
In organic chemistry, the Murai reaction is an organic reaction that uses C-H activation to create a new C-C bond between a terminal or strained internal alkene and an aromatic compound using a ruthenium catalyst. The reaction, named after Shinji ...
, which involves the insertion of alkenes into a C-H bond of acetophenone
Acetophenone is the organic compound with the formula C6H5C(O)CH3. It is the simplest aromatic ketone. This colorless, viscous liquid is a precursor to useful resins and fragrances.
Production
Acetophenone is formed as a byproduct of the cumene ...
. The keto group directs the regiochemistry, stabilizing an aryl intermediate.
When catalyzed by palladium carboxylates, a key step is electrophilic aromatic substitution
Electrophilic aromatic substitution (SEAr) is an organic reaction in which an atom that is attached to an aromatic ring, aromatic system (usually hydrogen) is replaced by an electrophile. Some of the most important electrophilic aromatic substitut ...
to give a Pd(II) aryl intermediate. Gold behaves similarly. Hydropyridination is a similar reaction, but entails addition of a pyridyl-H bond to alkenes and alkynes.{{cite journal , doi=10.1021/acs.organomet.5b01021, title=Chromium-Catalyzed Regioselective Hydropyridination of Styrenes, year=2016, last1=Li, first1=Yuexuan, last2=Deng, first2=Gongda, last3=Zeng, first3=Xiaoming, journal=Organometallics, volume=35, issue=5, pages=747–750
See also
*Vinylation In organic chemistry, vinylation is the process of attaching a vinyl group () to a substrate. Many organic compounds contain vinyl groups, so the process has attracted significant interest, especially since the reaction scope includes substituted ...
, the process of affixing a vinyl group
In organic chemistry, a vinyl group (abbr. Vi; IUPAC name: ethenyl group) is a functional group with the formula . It is the ethylene (IUPAC name: ethene) molecule () with one fewer hydrogen atom. The name is also used for any compound contai ...
References