Juan Vázquez

Simple and efficient conversion of N,N-dimethylhydrazones and aldehydes to nitriles.

Aldehyde N,N-dimethylhydrazones undergo facile oxidative cleavage to nitriles on reaction with magnesium monoperoxyphtalate hexahydrate (MMPP)

Synthesis of Enantiopureα-Alkoxy-α-Trifluoromethyl Aldehydes and Carboxylic Acids from Trifluoromethyl Ketones

Formaldehyde dialkylhydrazones behave as neutral d1 synthons in their uncatalyzed reaction with trifluoromethyl ketones (see reaction). Both racemic and optically pure 1,2-adducts were obtained in good yields. Efficient deprotection of the hydrazone moiety afforded interesting fluorinated quaternary compounds such as 1 and 2.

Formaldehyde dimethylhydrazone: A new neutral reagent for nucleophilic hydroformylation and hydrocyanation

Abstract The readily available title compound smoothly adds to nitroolefins without any need of base or catalysis, giving β-nitrodimethylhydrazones 3 in high yields. Michael adducts 3 have been successfully transformed into β-nitroaldehydes by ozonolysis and in β-nitronitriles in excellent yields by treatment with MMPP. Therefore, formaldehyde dimethylhydrazone behaves as a new neutral formyl anion and cyanide equivalent, introducing a functionalized carbon unit β to the nitro group of a nitroolefin. Good yields and high stereoselectivities were obtained in the addition of 1 to a nitroolefin group within sugar derivatives, and no epimerization was observed in the cleavage of the dimethylhydrazone group.

Synthese von enantiomerenreinen α‐Alkoxy‐ α‐trifluormethylaldehyden und ‐carbonsäuren aus Trifluormethylketonen

Formaldehyd-dialkylhydrazone sind die d1-Reagentien der Wahl, um aus Trifluormethylketonen ohne Katalysatorbeigabe die 1,2-Addukte zu erhalten (siehe Schema). Sowohl racemische als auch optisch reine Derivate waren in guten Ausbeuten zuganglich. Die effektive Abspaltung der Hydrazon-Schutzgruppe fuhrte zu interessanten fluorierten Verbindungen wie 1 und 2.

Diastereo- and enantioselective synthesis of 2,8-dioxabicyclo[3.3.0]octan-3-one derivatives

An efficient asymmetric synthesis of 4-substituted (1S,4S,5R)-2,8-dioxabicyclo[3.3.0]octan-3-one derivatives (de 98%, ee = 80–>98%) in good overall yields is reported by a stepwise Michael addition–α-alkylation and subsequent hydrolytic domino reaction protocol employing formaldehyde SAMP-hydrazone as a neutral formyl anion equivalent and 5,6-dihydro-2H-pyran-2-one as a Michael acceptor.

Asymmetric michael addition of formaldehyde N, N-dialkylhydrazones to alkylidene malonates

Enantiopure formaldehyde N,N-dialkylhydrazones 1 smoothly react with prochiral alkylidene malonates 2 in the presence of MgI2 to afford the corresponding Michael adducts 3 in excellent yields and good diastereoselectivities; direct racemization-free BF3.OEt2-catalyzed thiolysis of the hydrazone C=N bond affords the corresponding dithioketals 7 in optically pure or enantiomerically enriched form.

Asymmetric mannich-type addition of ketene silyl acetals and thioacetals to N,N-dialkylhydrazones

The choice of the 2,6-diphenylpiperidine moiety as the N,N-dialkylamino auxiliary in simple aliphatic dialkylhydrazones and the use of scandium triflate as the catalyst in aqueous media appear as the key strategies that enable the highly diastereoselective nucleophilic addition of ketene silyl acetals and thioacetals. The reaction proceeds to afford the expected adducts in high yields (88-98%) and diastereomeric ratios of up to 99:1. N-N bond cleavage of adducts affords enantiomerically pure β-amino esters.