Formyl cyclopropanes

Miscellaneous Iminium Catalyzed Transformations The enantioselective construction of three-membered hetero- or carbocyclic ring systems is an important objective for practitioners of chemical synthesis in academic and industrial settings. To date, important advances have been made in the iminium activation realm, which enable asymmetric entry to a-formyl cyclopropanes and epoxides. In terms of cyclopropane synthesis, a new class of iminium catalyst has been introduced, providing the enantioselective stepwise [2 + 1] union of sulfonium ylides and ot,p-unsaturated aldehydes.As shown in Scheme 11.6a, the zwitterionic hydro-indoline-derived catalyst (19) enables both iminium geometry control and directed electrostatic activation of sulfonium ylides in proximity to the incipient iminium reaction partner. This combination of geometric and stereoelectronic effects has been proposed as being essential for enantio- and diastereocontrol in forming two of the three cyclopropyl bonds. 

Bode and co-workers further extended redox esterification to include carbon-carbon bond breaking of formyl-cyclopropanes [113]. Both esters and thioesters are formed in high yield and good enantioselectivities (Scheme 31). The M-mesityl substituted triazolium salt 191 proved to be the most efficient pre-catalyst providing complete suppression of the benzoin reaction. Electron-deficient substituents, such as phenyl ketone, readily provide ester formation. 

Table 1. Formylated Cyclopropanes 7 and Cyclopropanes 8 by Cobalt and Manganese Carbonyl Hydride Mediated Hydroformylation/Hydrogenation of Cyclopropenes ...

Formylated Cyclopropanes by Hydroformylation of Cyclopropenes in Detergent Media General Procedure ... 

Tricarbonyliron complexes of conjugated trienes react with diazoalkanes at the free (uncom-plexed) double bond. In the synthesis of dimethyl 2-formylcyclopropane-l, 1-dicarboxylate (48), the ceric ion served the double function of catalyzing the deazetization and removing the tricarbonyl iron protecting group. When the optically active iron carbonyl complex was used, the addition of diazomethane gave selectively one diastereomer and this was used to make optically active dimethyl 2-formylcyclopropane-l,1-dicarboxylate (>90% ee). A similar route was employed to make the optically active formyl cyclopropanes 49, precursors to optically active cis- and tran.v-chrysanthemic acids. 

H3C ch3 co-s-c2h5 H3C00C h5c2-oh/h2o 5 100 2,2-Dimethyl-3-methoxy-carbonyl-1 -formyl-cyclopropan 44 150b 192... 

Das sterisch stark gehinderte Lithium-hydro-tri-tert.-butyloxy-aluminat reagiert nicht mit aromatischen und aliphatischen Nitrilen. Dagegen wird Lithium-hydro-tributyl-oxy-aluminat bei der HcrstcIIung von Formyl-cyclopropan (89%) mit besonders gutem Erfolg angewendet. 

Scheme 7.88 NHC-catalyzed formal hetero-Diels-Alder reactions between formyl-cyclopropanes and chalcones reported by Chi.

Scheme 18.15 Extension of the redox opening of epoxyaldehyde, according to Bode and coworkers, to strained chiral formyl cyclopropanes.

N-formamide-based Lewis bases 956 formyl cyclopropanes 507... 

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