Petasis reagent: Difference between revisions

| ImageFile = Petasis_Reagent.png

| ImageName = Structural formula of the Petasis reagent

| ImageFile1 = Petasis-reagent-3D-balls.png

| ImageSize1 = 120px

| ImageName1 = Ball-and-stick model of the Petasis reagent

| IUPACName = bis(η⁵-cyclopentadienyl)dimethyltitanium

| OtherNames = dimethyl titanocene

| Section1 = {{Chembox Identifiers

| SMILES = C[Ti](C)(C)c.c1cccc1.c2cccc2

| CASNo = 1271-66-5

| RTECS =

| Section2 = {{Chembox Properties

| Formula = C₁₂H₁₆Ti

| MolarMass = 208.13 g/mol

| Section7 = {{Chembox Hazards

| ExternalMSDS =

| MainHazards = Irritant, incompatible with water and oxidizing agents

| FlashPt =

| RPhrases

| SPhrases =

| Section8 = {{Chembox Related

| OtherCpds =

The '''Petasis reagent''' (not to be confused with the [[Petasis reaction]]) 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 = [[J. Am. Chem. Soc.]] | volume = 112 | issue = 17 | pages = 6392–6394 | doi = 10.1021/ja00173a035}}</ref> Cp₂TiMe₂, readily prepared by the reaction of [[methylmagnesium chloride]]<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 [[methyllithium]]<ref>{{cite journal | author = Claus, K.; Bestian, H. | journal = [[Justus Liebigs Ann. Chem.]] | 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 [[titanocene dichloride]]:

: Cp₂TiCl₂ + 2 "Me^&minus;" &rarr; Cp₂TiMe₂ + 2 Cl^&minus;

It is used for transforming carbonyl groups to terminal alkenes, much like the [[Tebbe reagent]] or [[Wittig reaction]]. 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 = [[Tetrahedron (journal)|Tetrahedron]] | 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 active olefinating reagent, Cp₂TiCH₂, is prepared by heating the Petasis reagent in toluene or THF to 60 °C.

The reaction mechanism is very similar to that of the Tebbe reagent, first yielding a titanium [[carbene]] 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>

{{reflist}}

[[Category:Coordination compounds]]

[[Category:Metallocenes]]

[[de:Petasis-Reagenz]]

[[ja:ペタシス試薬]]

[[nl:Dimethyltitanoceen]]