Carbonyl ylides aldehyde derivation

Wenkert and Khatuya (51) examined the competition between direct insertion of a carbene into furan (via cyclopropanation) and ylide formation with reactive side-chain functionality such as esters, aldehydes, and acetals. They demonstrated the ease of formation of aldehyde derived carbonyl ylides (Scheme 4.30) as opposed to reaction with the electron-rich olefin of the furan. Treatment of 3-furfural (136) with ethyl diazoacetate (EDA) and rhodium acetate led to formation of ylide 137, followed by trapping with a second molecule of furfural to give the acetal 138 as an equal mixture of isomers at the acetal hydrogen position. 

Various other [3 + 2] cycloadditions, affording chiral, anellated C6o derivatives with stereogenic centers in the addends are reported in literature. The products were generally obtained as racemates and resulted from reaction of buckminsterfullerene with species like 2,3-disubstituted 2//-azirincs (via nitrile ylides [under direct irradiation] or via 2-azaallenyl radical cations [sensitization by photoinduced electron transfer]),365 1-substituted 5-diazopentane-1,4-diones (via cyclic carbonyl ylides),366 7-alkylidene-2,3-diazabicyclo[2.2.1] hept-2-ene (via a diradicaloid trimethylenemethane derivative),367 1-benzylpy-razolidine-3-ones in the presence of aldehydes (via pyrazolidinium ylides),368 2-trifluoromethyl-2,5-dihydro-l,3-oxazol-5-ones (via nitrile ylides),369 nitro-alkanes in the presence of triethylamine and trimethylsilyl chloride (via N-silyloxynitrones),370 or dv-HOCH2 CH=C H C H 2 OCO 2 H( in the presence of... 

Finally, carbenoid species can be used as the carbon donor in aldehyde epoxidations. Thus, the rhodium carbenoid derived from the cyclic diazoamide 49 and rhodium(II) acetate reacts stereo selectively with aryl aldehydes to provide spiro-indolooxiranes 50 with Z-stereochemistry. The reaction is believed to proceed via the formation of a carbonyl ylide 51, which undergoes stereospecific thermal conrotatory electrocyclization to form the observed epoxide <04SL639>. 

One recent example of applying this process was reported by Johnson et al. for the preparation of furan derivatives (Scheme 16.12) [19]. This reaction involved the rhodium(II)-catalyzed intermolecular generation of carbonyl ylides A or B from diazosulfone (18) and aldehydes 19 or 21, respectively. The 1,3-dipolar cycloaddition of the resulting carbonyl ylides with an intramolecular tethered alkyne moiety or dimethyl acetylenedicarboxylate (DMAD, an intermolecular process), followed by elimination of phenylsulfinic acid, could access furan derivatives. 

They also reported high levels of enantioselection for the inter-molecular cycloadditions of ester-derived carbonyl ylides with DMAD (up to 93% ee, Rh2(S-PTTL)4) (Scheme 7.22) [58] and a-diazo ketone-derived carbonyl ylides with aromatic aldehydes (up to 92% ee, Rh2(S-BTPV)4) (Scheme 7.21) [59]. Dirhodium (II) tetrakis[A -tetrachIorophthaIoyI-(S)-ferf-Ieucinate], Rh2( 5-TCPTTL)4, was found to be an exceptionally effective catalyst for tandem carbonyl ylide formation/cycloaddition reactions of... 

Sulfur ylides are a classic reagent for the conversion of carbonyl compounds to epoxides. Chiral camphor-derived sulfur ylides have been used in the enantioselective synthesis of epoxy-amides <06JA2105>. Reaction of sulfonium salt 12 with an aldehyde and base provides the epoxide 13 in generally excellent yields. While the yield of the reaction was quite good across a variety of R groups, the enantioselectivity was variable. For example benzaldehyde provides 13 (R = Ph) in 97% ee while isobutyraldehyde provides 13 (R = i-Pr) with only 10% ee. These epoxy amides could be converted to a number of epoxide-opened... 

The difluoromethylene ylides react with carbonyl derivatives (aldehyde, lactone) to afford gem-difluoromethylene compounds.They are generated starting from halogenodifluoromethane with triphenylphosphine (or trisaminophosphine) or starting from zinc and a phosphonium salt (or a phosphine oxide)." ° ... 

These compounds come from methylenation reactions of the corresponding carbonyl derivative by means of an ylide. Several experimental conditions have been described. In most cases, CF2Br2 and HMPT (hexamethyl phosphorotriamide) are employed. The reaction occurs with aldehydes as well as with ketones in the furanose and pyranose series. The reaction can also be performed with lactones the fluoromethyl group is then introduced in the anomeric position. With these substrates, the Julia olefmation, which uses difluoromethyl sulfone, has also been reported to be an efficient method. Some examples of these reactions are shown in Figure 6.24. 

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