Carbonyls cyclopropanation

Thermal decarbonylation of (304) affords methylenecyclopropanes (305), which rearrange further (Scheme 43) by a path that is dependant on the substituent. Compound (304 R = OSiMc3) does not lead to carbonyl cyclopropane. ... 

The last group of reactions uses ring opening of carbonyl or 1-hydroxyalkyl substituted cyclopropanes, which operate as a -synthons. d -Synthons, e.g. hydroxide or halides, yield 1,4-disubstituted products (E. Wenkert, 1970 A). (1-Hydroxyalkyl)- and (1-haloalkyl)-cyclopropanes are rearranged to homoallylic halides, e.g. in Julia s method of terpene synthesis (M. Julia, 1961, 1974 S.F. Brady, I968 J.P. McCormick, 1975). 

Another widely used route to cyclopropanes involves the addition of sulfoniutn ylides to a,/3-unsaturated carbonyl compounds (S.R. Landor, 1967 R. Sowada, 1971 C.R. Johnson, I973B, 1979 B.M. Trost, 1975 A). Non-activated double bonds are not attacked. Sterical hindrance is of little importance in these reactions because the C—S bond is extraordinarily long... 

In similar reactions, (12) with carbon—carbon double bonds that are conjugated with carbonyl groups gives cyclopropane derivatives (eq. 24) (48) ... 

Cyclopropanes from unsaturaled carbonyl compounds via pyraaolines by catalytic pyrolysis... 

In the presence of suitable a,/5-unsaturated carbonyl compounds (3) the nucleophilic methylide (2) undergoes conjugate addition followed by expulsion of dimethyl sulfoxide to give cyclopropanes (5). 

The Corey-Chaykovsky reaction entails the reaction of a sulfur ylide, either dimethylsulfoxonium methylide (1, Corey s ylide, sometimes known as DMSY) or dimethylsulfonium methylide (2), with electrophile 3 such as carbonyl, olefin, imine, or thiocarbonyl, to offer 4 as the corresponding epoxide, cyclopropane, aziridine, or thiirane. ... 

Epoxidation of aldehydes and ketones is the most profound utility of the Corey-Chaykovsky reaction. As noted in section 1.1.1, for an a,P-unsaturated carbonyl compound, 1 adds preferentially to the olefin to provide the cyclopropane derivative. On the other hand, the more reactive 2 generally undergoes the methylene transfer to the carbonyl, giving rise to the corresponding epoxide. For instance, treatment of P-ionone (26) with 2, derived from trimethylsulfonium chloride and NaOH in the presence of a phase-transfer catalyst Et4BnNCl, gave rise to vinyl epoxide 27 exclusively. ... 

Due to the high reactivity of sulfonium ylide 2 for a,P-unsaturated ketone substrates, it normally undergoes methylene transfer to the carbonyl to give the corresponding epoxides. However, cyclopropanation did take place when 1,1-diphenylethylene and ethyl cinnamate were treated with 2 to furnish cyclopropanes 53 and 54, respectively. 

Dimethylsulfoxonium methylide (1) is the reagent of choice for the cyclopropanation of a,p-unsaturated carbonyl substrates. The reaction is generally carried out at more elevated temperatures in comparison to that of 2, although exceptions exist. The method works for 0 ,P-unsaturated ketones, esters and amides. Representative examples are found in transformations of 2(5//)-furanone 55 to cyclopropane 56 and 0 ,P-unsaturated Weinreb amide 57 to cyclopropane 58. ... 

Cyclopentene-l-dithiocarboxylic acid, 2-amino-meta complexes, 2, 800 Cyclophane chlorophylls, 3, 58 Cyclophane hemes iron complexes, 4,1269 Cyclophosphazenes metal complexes, 2, 81 Cyclopropane carbonylation... 

These carbene (or alkylidene) complexes are used for various transformations. Known reactions of these complexes are (a) alkene metathesis, (b) alkene cyclopropanation, (c) carbonyl alkenation, (d) insertion into C-H, N-H and O-H bonds, (e) ylide formation and (f) dimerization. The reactivity of these complexes can be tuned by varying the metal, oxidation state or ligands. Nowadays carbene complexes with cumulated double bonds have also been synthesized and investigated [45-49] as well as carbene cluster compounds, which will not be discussed here [50]. 

Metalloporphyrins have proved their efficiency as ruthenium carbonyl hg-ands for the enantioselective cyclopropanation of styrene [50,51]. 

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