Synthesis cyclopropane

FREUNO-GUSTAVSON Cyclopropane Synthesis Cyclopropane synthesis from 1,3-dihaloalkenes with metals... 

PFAU - PLATTNER Cyclopropane synthesis DIazoalkane insertion Into olelins wtth lormation of cyclopropanes or ring enlargement ol aromatics to cydoheptatnenes see also lormation ol pyrazoHnes (von Pechman). 

W I 0 E Q U I S T Cyclopropane synthesis Tetracyanocyclopropane synthesis from bromomalonitnie and ketones... 

Cyclopropane synthesis, 107 Cyclopropyllithium, 64, 72 17a-Cyclopropyl-3-niethoxyestra-l, 3,5 (10)-trien-17 -ol, 72... 

Reagent-controlled asymmetric cyclopropanation is relatively more difficult using sulfur ylides, although it has been done. It is more often accomplished using chiral aminosulfoxonium ylides. Finally, more complex sulfur ylides (e.g. 64) may result in more elaborate cyclopropane synthesis, as exemplified by the transformation 65 66 ... 

Cyclopentenones reactions of 835, 836 synthesis of 620 Cyclopropanation 648 Cyclopropanecarboxylates, synthesis of 318 Cyclopropanes, synthesis of 772, 773, 785-787... 

H. E. Simmons and R. D. Smith of the DuPont Company had developed a useful cyclopropane synthesis by reacting a zinc-copper couple with an alkene. 

An alternative cyclopropane synthesis via an active methylene compound can also be enhanced by sonication [110]. The number of examples quoted in the literature is low but in the case of ethyl cyanoacetate and dibromoethane sonicated with potassium carbonate and polyethylene glycol in ethylene dichloride the expected cyclopropane is generated in 85 % yield (Eq. 3.19). 

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. 

These complexes can be isolated in some cases in others they are generated in situ from appropriate precursers, of which diazo compounds are among the most important. These compounds, including CH2N2 and others, react with metals or metal salts (copper, palladium, and rhodium are most commonly used) to give the carbene complexes that add CRR to double bonds.1063 Optically active complexes have been used for enantioselective cyclopropane synthesis.1064... 

SAMPLE SOLUTION (a) In a cyclopropane synthesis using the Simmons-Smith reagent, you should remember that a CH2 unit is transferred. Therefore, retro-synthetically disconnect the bonds to a CH2 group of a three-membered ring to identify the starting alkene. 

An asymmetric cyclopropane synthesis has been achieved by the addition-cyclization reaction of a chiral a,/ -unsaturated sulfoxide with a Grignard reagent (equation 32)49. 

KISHNEK CYCLOPROPANE SYNTHESIS. Formation of cyclopropane derivatives by deeompoxiiion of pyra/olines formed by reacting tr/l-unsiiiurated kelones or aldehydes with hydrazine. 

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