Petasis olefination

Meurer, E. C., Santos, L. S., Pilli, R. A., Eberlin, M. N. Probing the Mechanism of the Petasis Olefination Reaction by Atmospheric Pressure Chemical Ionization Mass and Tandem Mass Spectrometry. Org. Lett. 2003, 5, 1391-1394. 

BTF can be used for some important transition metal catalyzed reactions, such as the Grubbs olefin-metathesis reaction [64] (11.1), the Petasis olefination [65]... 

Table 2.1 lists some of the mechanistic studies of organic and organometallic reactions reported in the literature by ESI-MS. All sorts of reactions have been successfully explored in the gas phase, such as the Baylis-Hillman reaction [211-213], C-H or N-H activation [214—219], cydopropanation reaction [220], Diels-Alder reactions [221], displacement reactions [222], electrophilic fluorination [223, 224], Fischer indole synthesis [225], Gilman reaction [226, 227], Grubbs metathesis reaction [228-231], Heck reaction [194], methylenation [232], oxidation [233, 234], Petasis olefination reaction [235], Raney Nickel-catalyzed coupling [236], ruthenium... 

Petasis olefination-, oxatitanacyde intermediates were transferred from solution to the gas phase and detected the CID behavior of the intermediates fully supports the Hughes mechanism. Electron tranfer-initiated Dids-Alder reactions the transient radical cations were detected. 

Meurer, E.C., Santos, LS., PiUi, R.A., and Eberlin, M.N. (2003) Probing the mechanism of the petasis olefination reaction by atmospheric pressure chemical ionization mass and tandem mass spectrometry. Org. Lett., 5, 1391-1394. 

Methylenation of tertiary amides utilizing Petasis reagent, including A -acyl heterocycles, gives enamines. From the corresponding a-lactam 92, and P-lactams 89, methyleneaziridine 93 and methylenetidine 91 were synthesized via Petasis olefination. ... 

Another route via hydrocobaltation of ynone and ynoate led easily to 1-cobaloxime enone or enoate. 1-cobaloxime diene 180 was obtained after Peterson or Petasis olefination (Scheme 26). ... 

Both the Tebbe and Petasis reagents, Cp2CH2ClAlMe2 and Cp2TiMe2, effect the direct conversion of alkenic esters to dihydropyrans. This olefin metathesis has been successfully applied to the synthesis of complex polyether frameworks <96JA1565,96JA10335>. 

A limitation to the use of the Tebbe reagent 93 was observed during the attempted conversion of substrates 139 and 142 to the tricyclic systems 141 and 144 respectively (Scheme 21). The major products from these reactions were olefinic alcohols 140 and 143. These products presumably resulted from sequential hydrolysis and olefination of the initially formed cyclic enol ethers. The problem associated with these sensitive substrates was overcome through use of the less Lewis-acidic Petasis reagent 110, which provided access to the desired products 141 and 144 [34a]. 

Scheme 21. Titanium-mediated metathesis strategy for the synthesis of cyclic enol ethers and hydroxy olefins, (a) Tebbe reagent (93), THF, reflux, 41% (140), 41% (143) (b) Petasis reagent (110), THF, reflux, 60% (141), 30% (144) (Nicolaou et al.) [34a]...

Conceptually this new three-component reaction resembles the methods applied by Steglich, Enders et al. [8a] and Yamamoto et al. [8b], who treated the preformed iminoesters 26 and 29 at low temperature with the electron-rich olefins 27 and 30, respectively [9]. However, the use of boronic acid derivatives appears to be a versatile method with a great deal of potential. As Petasis and Zavialov note at the end of their paper, unprotected amino acids and peptides, aryl boronic acids, and chiral boronates can also participate in their three component condensation [7a]. Transition metal catalysis also... 

Similarly, the C22-C26 fully substituted central tetrahydropyran ring of phorboxazole was prepared using the modified Petasis-Ferrier rearrangement. Based on the known mechanistic model, the enol acetal moiety of the rearrangement substrate required the (Z)-configuration. The synthesis of this enol ether was not possible with either the Takai- or Petasis-Tebbe oiefinations. Utilization of the Type-ll Julia olefination afforded the desired enol acetal, but with no /Z selectivity. Upon treatment of these enol ethers with Me2AICI, the rearrangement afforded only the desired tetrahydropyran in excellent yield. 

Petasis, N. A., Bzowej, E. I. Titanium-mediated carbonyl olefinations. 1. Methylenations of carbonyl compounds with dimethyltitanocene. J. Am. Chem. Soc. 1990,112, 6392-6394. 

The Petasis reagent reacts with aldehydes, ketones, and esters to afford terminal olefins. In addition, tliis reagent enjoys greater air stability than the Tebbe reagent. 

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