Palladium cyclobutanones

TO PALLADIUM-CATALYZED ASYMMETRIC BAEYER-VILUGER OXIDATION OF PROCHKAL CYCLOBUTANONES. 256... 

SYNTHESIS OF 2-(PHOSPHINOPHENYL)PYRINDINE LIGAND AND ITS APPLICATION TO PALLADIUM-CATALYZED ASYMMETRIC BAEYER-VILLIGER OXIDATION OF PROCHIRAL CYCLOBUTANONES... 

Table 7.1 Asymmetric Baeyer-ViUiger oxidation of several cyclobutanones using chiral palladium complex"...

Other methods have appeared, but have been less frequently used, e.g. chromium chloride in acetone 140- 143 (y/yfe infra) and dissolving alkali-metal reductions.144,145 Hydrogenolysis with palladium/hydrogen has also given the monoreduced cyclobutanone.99,100... 

Linkers that enable the preparation of y-lactones by cleavage of hydroxy esters from insoluble supports are discussed in Section 3.5.2. Resin-bound y-lactones have been prepared by Baeyer-Villiger oxidation of cyclobutanones [39], by intramolecular addition of alkyl radicals to oximes [48], by electrophilic addition of resin-bound sele-nenyl cyanide or bromide to 3,y-unsaturated acids (Figure 9.2 [100]), and by palladium-mediated coupling of resin-bound aryl iodides with allenyl carboxylic acids (Entry 10, Table 5.7 [101]). 

It is well known that cyclobutanones can be transformed to cyclopentane derivatives directly with diazomethane or indirectly via the cyanohydrins218> 228), or with tris(phe-nylthio)methyllithium 219,220), but in many cases the reactions are not regioselective and lead to different regioisomers. Cyclobutyl ketones lead to substituted cyclopentanones in highly acidic media 226 and the synthesis of cyclopentanones from methylene-cyclobutanes requires a palladium catalyst 227). 

Thus, traMi-3-alkyl-6-(phthalimido)cyclopentenes were prepared in excellent to modest yields from the corresponding tran -chloroalkene by the palladium coupling reaction [84d]. Inexpensive and efficient Pd-TMG systems, Pd(OAc)2-TMG or PdC -TMG, have been developed for the Heck reaction of an olefin with an aryl halide, in which TMG (1) acts as a ligand [84e]. In the reaction of iodobenzene with butyl acrylate the turnover numbers were up to 1000000. TMG (1) was used as a base for the palladium catalysed asymmetric Wagner-Meerwein shift of nonchiral vinylcyclopropane and cyclobutane derivatives leading to asymmetric synthesis of cyclobutanones, cyclopentenones, y-butyrolactones and 5-valerolactones [85] (Scheme 4.34). Replacement of TMG (1) with an inorganic bases such as lithium or cesium carbonate resulted in little effect. 

Substituted cyclobutanones have been converted to enantioenriched y-lactones by palladium-catalysed BV oxidation, using chiral phosphino-oxazoline ligands, giving yields up to 99% and 81% ee, rising to >93% ee through a single recrystallization. ... 

Transition metal alkoxides of tert-cyclobutanols undergo ring opening by P-carbon elimination to generate ketones that are metalated at the y-position these can be utilized in many functionalization reactions. Palladium, rhodium, and nickel have been the most studied metals in these transformations. Useful transition metal cyclobutanolates are generated from either cyclobutanones or cyclobutanols. 

Hydroxyphenyl)cyclobutanone 35 reacted with bromobenzene in the presence of a palladium catalyst to afford 4-(arylmethyl)-3,4-dihydrocoumarin 36 (Scheme 3.15) [26]. 

Palladium-catalyzed reaction of cyclobutanone 0-benzoyloximes proceeded via oxidative addition of the N-O bond of the oxime to Pd(0) and P-carbon elimination of the resulting cyclobutylideneamidopalladium(II), affording a reactive alkylpalladium(II) species [48]. The a,P-unsaturated nitrile 64 was obtained when 3-phenylcyclobutanone 0-benzoyloxime (65) was reacted in the presence of a Pd(0)-BINAP (2,2 -bis(diphenylphosphino)-l,l -binaphthyl) catalyst (Scheme 3.37). 

Palladium-catalyzed intramolecular reactions of 3-(2-disilanylphenyl)cyclo-butanone 87 resulted in C-C/Si-Si o-bond metathesis to give acylsilane 88 (Scheme 3.48) [57]. a-Bond metathesis was proposed to proceed via a pal-ladium(IV) intermediate, which is formed by the oxidative addition of the cyclobutanone C-C bond to a bis(silyl)palladium(II) species. 

Cyclopropanol 74 underwent asymmetric ring expansion via 1,2-alkyl migration upon treatment with a chiral palladium catalyst to furnish the cyclobutanone... 

Ito K, Ishii A, Kuroda T, Katsuki T. Asymmetric Baeyer-Villiger oxidation of prochiral cyclobutanones using a chiral cationic palladium(II) 2-(phosphinophenyl)pyridine complex as catalyst. Synlett 2003 643-646. 

Petersen KS, Stoltz BM. Palladium-catalyzed, asymmetric Baeyer-Villiger oxidation of prochiral cyclobutanones with PHOX ligands. Tetrahedron 2011 67 4352- 357. 

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