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Wittig reaction compatible functional

Intramolecular Wittig reactions can be used for the preparation of cyclic alkenes. The formation of the phosphonium ylide must be compatible with other functionality in the molecule and thus stabilized ylides are used most commonly. Wittig reactions with carbonyl groups other than aldehydes or ketones, such as carboxylic esters, are known. For example, a route to the indole or penem ring systems uses a carboxylic amide or a thioester respectively as the intramolecular electrophile (2.77). [Pg.137]

Generally the conditions required to carry out the Horner-Wittig reaction are not compatible with sensitive functional groups such as hydroxy-, nitro-, and keto-aldehydes these residues must normally be protected. However, the use of a heterogeneous base such as K CO in either aqueous or organic media allows the condensation of these sensitive substrates with activated phosphorates to take place directly. The synthesis of Royal Jelly acid from 8-... [Pg.397]

As the complexity of substrates being submitted to the Wittig reaction dramatically increased, gentler reactions conditions were required to accommodate greater inter-functional group compatibility. Thus the nature of the base necessary to form the ylide was studied. Roush and coworkers reported the successful use of lithium chloride with amine bases (DBU or DIPEA) for base sensitive aldehydes or phosphonates. One example cited involved the coupling of phosphonate 62 with aldehyde 63 to afford triene 64 in good yield. This stands in sharp contrast to when NaH was used and no desired product was observed. [Pg.597]

Molander has recently reported the compatibility of organotrifluoroborates with the Wittig and HWE reactions. The value in this transformation can be realized in light of the increased use of this functional group in palladium cross-coupling reactions. This approach allows one to structurally elaborate a relatively sensitive moiety before conducting, for example, a Suzuki reaction. Thus, aldehyde 137 afforded alkene 139 when exposed to ylide 138. [Pg.607]


See other pages where Wittig reaction compatible functional is mentioned: [Pg.45]    [Pg.98]    [Pg.94]    [Pg.135]    [Pg.473]    [Pg.92]    [Pg.579]    [Pg.26]    [Pg.13]   


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