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{{Distinguish|Petasis reaction}}
{{chembox {{chembox
| Verifiedfields = changed
| ImageFile = Petasis_Reagent.png
| Watchedfields = changed
| verifiedrevid = 404448904
| ImageFile = Petasis reagent V1.svg
| ImageSize = 120px | ImageSize = 120px
| ImageName = Structural formula of the Petasis reagent | ImageName = Structural formula of the Petasis reagent
| ImageFile1 = Petasis-reagent-3D-balls.png | ImageFile1 = Petasis-reagent-3D-balls.png
| ImageSize1 = 120px | ImageSize1 = 120px
| ImageName1 = Ball-and-stick model of the Petasis reagent | ImageName1 = Ball-and-stick model of the Petasis reagent
| IUPACName = bis(η<sup>5</sup>-cyclopentadienyl)dimethyltitanium | IUPACName = Bis(η<sup>5</sup>-cyclopentadienyl)dimethyltitanium
| OtherNames = dimethyl titanocene | OtherNames = Dimethyltitanocene
| Section1 = {{Chembox Identifiers |Section1={{Chembox Identifiers
| SMILES = C(C)(C)c.c1cccc1.c2cccc2 | SMILES = (C)(C).c1ccc1.c2ccc2
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
⚫ | CASNo = 1271-66-5
| ChemSpiderID = 34981143
⚫ | RTECS =
| InChI = 1/2C5H5.2CH3.Ti/c2*1-2-4-5-3-1;;;/h2*1-5H;2*1H3;/q2*-1;;;+2/r2C5H5.C2H6Ti/c2*1-2-4-5-3-1;1-3-2/h2*1-5H;1-2H3/q2*-1;+2
| InChIKey = AFEQRLILWYRIDQ-MEMJIDHRAL
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/2C5H5.2CH3.Ti/c2*1-2-4-5-3-1;;;/h2*1-5H;2*1H3;/q2*-1;;;+2
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
| StdInChIKey = AFEQRLILWYRIDQ-UHFFFAOYSA-N
| PubChem = 71308256
| EINECS = 679-889-8
| CASNo_Ref = {{cascite|correct|??}}
⚫ | CASNo = 1271-66-5
⚫ | RTECS =
}} }}
| Section2 = {{Chembox Properties |Section2={{Chembox Properties
| Formula = C<sub>12</sub>H<sub>16</sub>Ti | Formula = C<sub>12</sub>H<sub>16</sub>Ti
| MolarMass = 208.13 g/mol | MolarMass = 208.13 g/mol
}} }}
| Section7 = {{Chembox Hazards |Section7={{Chembox Hazards
| ExternalMSDS = | ExternalSDS =
| MainHazards = Irritant, incompatible with water and oxidizing agents | MainHazards = Irritant, incompatible with water and oxidizing agents
| FlashPt = | FlashPt =
| GHSPictograms = {{GHS02}}{{GHS07}}{{GHS08}}
| RPhrases
| SPhrases = | GHSSignalWord = Danger
| HPhrases = {{H-phrases|225|304|315|319|332|360|370|372}}
| PPhrases = {{P-phrases|}}
}} }}
| Section8 = {{Chembox Related |Section8={{Chembox Related
| OtherCpds = | OtherCompounds =
}} }}
}} }}
The '''Petasis reagent''' (not to be confused with the ]) is dimethyl titanocene,<ref>{{cite journal | author = N. A. Petasis and E. I. Bzowej | title = Titanium-mediated carbonyl olefinations. 1. Methylenations of carbonyl compounds with dimethyltitanocene | year = 1990 | journal = ] | volume = 112 | issue = 17 | pages = 6392–6394 | doi = 10.1021/ja00173a035}}</ref> Cp<sub>2</sub>TiMe<sub>2</sub>, readily prepared by the reaction of ]<ref>{{OrgSynth | author = Payack, J. F.; Hughes, D. L.; Cai, D.; Cottrell, I. F.; Verhoeven, T. R. | prep = v79p0019 | volume = 79 | pages = 19 | year = 2002 | title = Dimethyltitanocene}}</ref> or ]<ref>{{cite journal | author = Claus, K.; Bestian, H. | journal = ] | year = 1962 | volume = 654 | pages = 8 | doi = 10.1002/jlac.19626540103 | title = Über die Einwirkung von Wasserstoff auf einige metallorganische Verbindungen und Komplexe}}</ref> with ]:


The '''Petasis reagent''', named after Nicos A. Petasis, is an ] with the formula Cp<sub>2</sub>Ti(CH<sub>3</sub>)<sub>2</sub>.<ref>{{cite journal |author1=N. A. Petasis |author2=E. I. Bzowej |name-list-style=amp | title = Titanium-mediated carbonyl olefinations. 1. Methylenations of carbonyl compounds with dimethyltitanocene | year = 1990 | journal = ] | volume = 112 | issue = 17 | pages = 6392–6394 | doi = 10.1021/ja00173a035}}</ref> It is an orange-colored solid.
⚫ : Cp<sub>2</sub>TiCl<sub>2</sub> + 2 "Me<sup>&minus;</sup>" &rarr; Cp<sub>2</sub>TiMe<sub>2</sub> + 2 Cl<sup>&minus;</sup>


==Preparation and use==
⚫ It is used for transforming carbonyl groups to terminal alkenes, much like the ] or ]. Unlike the Wittig reaction, the Petasis reagent can react with a wide range of carbonyls, including aldehydes, ketones and esters.<ref>{{cite journal | doi = 10.1016/j.tet.2007.03.015 | title = Titanium carbenoid reagents for converting carbonyl groups into alkenes | author = Hartley, R. C.; Li, J.; Main, C. A.; McKiernan, G. J. | journal = ] | year = 2007 | volume = 63 | pages = 4825–4864}}</ref> The Petasis reagent is also more air stable than the Tebbe reagent, and can be isolated as a pure solid, or used directly as a solution in toluene-THF.
The Petasis reagent is prepared by the ] of ] or ]<ref>{{cite journal |author1=Claus, K. |author2=Bestian, H. | journal = ] | year = 1962 | volume = 654 | pages = 8–19 | doi = 10.1002/jlac.19626540103 | title = Über die Einwirkung von Wasserstoff auf einige metallorganische Verbindungen und Komplexe}}</ref> with ]:<ref>{{OrgSynth | author = Payack, J. F. | author2 = Hughes, D. L. | author3 = Cai, D. | author4 = Cottrell, I. F. | author5 = Verhoeven, T. R. | prep = v79p0019 | volume = 79 | pages = 19 | year = 2002 | title = Dimethyltitanocene}}</ref>


⚫ : Cp<sub>2</sub>TiCl<sub>2</sub> + 2 CH<sub>3</sub>MgCl → Cp<sub>2</sub>Ti(CH<sub>3</sub>)<sub>2</sub> + 2 MgCl<sub>2</sub>
The active olefinating reagent, Cp<sub>2</sub>TiCH<sub>2</sub>, is prepared by heating the Petasis reagent in toluene or THF to 60 °C.


⚫ This compound is used for the transformation of carbonyl groups to ]s. It exhibits similar reactivity to the ] and ]. Unlike the Wittig reaction, the Petasis reagent can react with a wide range of aldehydes, ketones and esters.<ref>{{cite journal | doi = 10.1016/j.tet.2007.03.015 | title = Titanium carbenoid reagents for converting carbonyl groups into alkenes |author1=Hartley, R. C. |author2=Li, J. |author3=Main, C. A. |author4=McKiernan, G. J. | journal = ] | year = 2007 | volume = 63 | pages = 4825–4864 | issue = 23}}</ref> The Petasis reagent is also very air stable, and is commonly used in solution with toluene or THF.
⚫ The reaction mechanism is very similar to that of the Tebbe reagent, first yielding a titanium ] which forms a four membered oxatitanacyclo and than releases the terminal alkene.<ref>{{cite journal | last1 = Meurer | first1 = Eduardo Cesar | last2 = Santos | first2 = Leonardo Silva | last3 = Pilli | first3 = Ronaldo Aloise | last4 = Eberlin | first4 = Marcos N. | title = Probing the Mechanism of the Petasis Olefination Reaction by Atmospheric Pressure Chemical Ionization Mass and Tandem Mass Spectrometry | journal = Organic Letters | volume = 5 | pages = 1391 | year = 2003 | doi = 10.1021/ol027439b}}</ref>

⚫ The Tebbe reagent and the Petasis reagent share a similar reaction mechanism. The active olefinating reagent, Cp<sub>2</sub>TiCH<sub>2</sub>, is generated in situ upon heating. With the organic carbonyl, this titanium ] forms a four membered oxatitanacyclobutane that releases the terminal alkene.<ref>{{cite journal | last1 = Meurer | first1 = Eduardo Cesar | last2 = Santos | first2 = Leonardo Silva | last3 = Pilli | first3 = Ronaldo Aloise | last4 = Eberlin | first4 = Marcos N. | title = Probing the Mechanism of the Petasis Olefination Reaction by Atmospheric Pressure Chemical Ionization Mass and Tandem Mass Spectrometry | journal = Organic Letters | volume = 5 | pages = 1391–4 | year = 2003 | doi = 10.1021/ol027439b | issue = 9 | pmid = 12713281}}</ref>

:]
:]
In contrast to the ], homologs of the Petasis reagent are relatively easy to prepare by using the corresponding alkyllithium instead of methyllithium, allowing the conversion of carbonyl groups to alkylidenes.<ref>{{Citation|last1=Petasis|first1=Nicos A.|title=Bis(cyclopentadienyl)dimethyltitanium|date=2012-03-15|encyclopedia=Encyclopedia of Reagents for Organic Synthesis|pages=rb126.pub3|editor-last=John Wiley & Sons, Ltd.|place=Chichester, UK|publisher=John Wiley & Sons, Ltd.|language=en|doi=10.1002/047084289x.rb126.pub3|isbn=978-0-471-93623-7|last2=Morshed|first2=M. Monzur|last3=Ahmad|first3=M. Syarhabil|last4=Hossain|first4=M. Mahmun|last5=Trippier|first5=Paul C.}}</ref>

==See also==
* ]
*]


==References== ==References==
{{reflist}} {{Reflist}}


{{Titanium compounds}}
{{Cyclopentadienide complexes}}
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