200408-50-0Relevant academic research and scientific papers
Formaldehyde dialkylhydrazones as neutral formyl anion and cyanide equivalents: Nucleophilic addition to conjugated enones
Diez,Fernandez,Gasch,Lassaletta,Llera,Martin-Zamora,Vazquez
, p. 5144 - 5155 (2007/10/03)
A versatile methodology for the nucleophihc formylation and cyanation of conjugated enones is reported. The procedure is based on the use of formaldehyde dimethylhydrazone, which, acting as a neutral formyl anion equivalent, adds to preformed trialkylsilyl-enone complexes. Both 4-(silyl- oxy)-3-enal hydrazones 3 or deprotected 4-oxo aldehyde monohydrazones 4 can be obtained at products depending on quenching conditions. In full analogy, an asymmetric version of the reaction using chiral formaldehyde SAMP- hydrazone as a neutral synthon of the chiral formyl anion has been developed, giving rise to the corresponding adducts 5 and 6 in good yields and with excellent diastereoselectivities (de 85-≤98%). Ozonolysis or HCl-mediated hydrolysis of adducts 4 and 6 readily affords racemic and optically enriched 4-oxo aldehydes 7, respectively. Additionally, high-yielding MMPP-oxidative cleavage of 4-oxo hydrazones 4 and 6 has been performed to obtain 4-oxo nitriles 8 in racemic and optically enriched forms, respectively. In this way, interesting chiral bifunctional building blocks, some of them bearing newly created stereogenic quaternary centers, have been efficiently synthesized.
