Cyclobutanones Baeyer-Villiger reaction

Cyclobutanone annulation onto a carbonyl group translates into y-butyrolactone annulation because of the facility of the Baeyer-Villiger reaction (Eq. 68 a)8). Indeed, the reaction proceeds sufficiently rapidly that even basic hydrogen peroxide effects the oxidation whereas, with less reactive carbonyl partners, peracids must be used. 

At this time, we can focus on the creation of the butenolide. Sulfur based methodoly allows simplification to the simple butanolide as in 170. While cyclobutanone spiroannulation of 171 followed by a Baeyer-Villiger reaction would create 170,... 

Another method for the asymmetric version of the Baeyer-Villiger reaction was presented by Lopp and coworkers in 1996 . By employing overstoichiometric quantities of Ti(OPr-t)4/DET/TBHP (1.5 eq./1.8 eq./1.5 eq.), racemic andprochiral cyclobutanones were converted to enantiomerically enriched lactones with ee values up to 75% and moderate conversions up to 40% (Scheme 171). Bolm and Beckmann used a combination of axially chiral C2-symmetric diols of the BINOL type as ligands in the zirconium-mediated Baeyer-Villiger reaction of cyclobutanone derivatives in the presence of TBHP (or CHP) as oxidant (Scheme 172) . With the in situ formed catalysts 233a-d the regioisomeric lactones were produced with moderate asymmetric inductions (6-84%). The main drawback of this method is the need of stoichiometric amounts of zirconium catalyst. 

The use of a chiral hydroperoxide as oxidant in the asymmetric Baeyer-Villiger reaction was also described by Aoki and Seebach, who tested the asymmetric induction of their TADOOH hydroperoxide in this kind of reaction98. Besides epoxidation and sulfoxidation, for which they found high enantioselectivities with TADOOH (60), this oxidant is also able to induce high asymmetry in Baeyer-Villiger oxidations of racemic cyclobutanone derivatives in the presence of DBU as a base and LiCl as additive (Scheme 174). The yields and ee values (in parentheses) of ketones and lactones are given in Scheme 174 as... 

Figure 4.8 Baeyer-Villiger reaction of cyclobutanone in fluorous media [196],...

Ding and co-workers reported the Baeyer-Villiger reaction of cyclobutanones by means of 23b, giving access to ylactones with high enantioselectivities (Equation 10.49) [95],... 

Small-ring ketones can relieve ring strain by undergoing Baeyer-Villiger reactions—this cyclobutanone (an intermediate in a synthesis of the perfumery compound ds-jasmone) is... 

When the ketone is cyclic, a cyclic ester, or lactone, is formed. Cyclobutanone is oxidized to a lactone by the Baeyer-Villiger reaction. 

The cyclobutanol (357) and the cyclobutanone (358) are both converted into the lactone (359) on chromic acid oxidation in either aqueous or aqueous acetic acid medium. " Other alkylated cyclobutanols and cyclobutanones behave similarly. Yields vary between 55 and 90% depending on the specific case. The regioselectivity of the reaction is the same as that in the Baeyer-Villiger reaction. Direct oxidation with chromic acid of the cyclobutanol (360), formed by photochemical cyclization of the ketone (361), gives the 1,4-dione (362) in 55% yield. This is a considerable improvement in terms of both time and yield over the previously used sequence of dehydration and cleavage. 

Although more than one century has gone by since its discovery in 1899, the Baeyer Villiger reaction is still far from being fully developed. In particular, there are only a few catalyst systems which afford products from the Baeyer-Villiger oxidation of 3-substituted cyclobutanones in more than 80% ee. The first example of the enantioselective Baeyer-Villiger oxidation of 3-substituted cyclobutanones catalysed by a chiral organocatalyst and 30%... 

Katsuki successfully appHed two different metal salen complexes in asymmetric Baeyer-Villiger reactions. Cationic cobalt complex 51 catalyzes the reaction between cyclobutanone 50 and UHP as oxidant to give lactone 46 with 77% ee in 72% yield [349], In the same transformation zirconium salen complex 52 affords the product with higher enantioselectivity (87% ee) (Scheme 9.5). Over 99% ee could be achieved in the conversion of tricyclic ketone 47 [350],... 

The Baeyer-Villiger oxidation of acyl-substituted cyclobutanones 1 is reported to be very slow with ordinary peracids such as 3-chloroperoxybenzoic acid24- 31 37 38 and peracetic acid.24,36 Generally, reaction times of several weeks are needed to obtain acceptable yields of acyloxycy-... 

Cyclobutanones are the only ketones that undergo Baeyer-Villiger rearrangements not only with peracids but even with alkaline H202 or alkaline ferf-BuOOH (Figure 11.35). In this case, the driving forces of two crucial reaction steps are higher than... 

Cyclobutanones are susceptible to Baeyer-Villiger oxidation. The epoxide (186) cannot be prepared by reacting the ketoalkene (185 equation 67) with MCFBA. Moderate, chemoselective epoxidation has been observed in the reaction of (185 equation 68) with ( -trichloroethylperoxycaib(Miic acid (190) prepared in situ from the triazole (189) and H2O2. ... 

Stereoselective epoxidation of alkenes, desymmetrization of maso-TV-sulfonylaziri-dines, Baeyer-Villiger oxidation of cyclobutanones, Diels-Alder reactions of 1,2-dihydropyridines, and polymerization of lactides using metal complexes of chiral binaphthyl Schiff-base ligands 03CCR(242)97. 

An important application of metal bis(perfluorooctanesulfonyl)amides in fluorous biphasic systems is the Baeyer-Villiger oxidation. Especially Sn[N(S02C8F17)2]4 could be reused more than four times in the Baeyer-Villiger oxidation of adamantone and cyclobutanone without significant decomposition of the catalyst (Equation 4.26). It was found that there was almost no difference for the formation rate of y-butyr-olactone between the first and fourth cycles within a 1 h reaction time, which showed that there was not only no loss of the catalyst, but also no decrease in catalytic activity during the repetition [47]. 

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