1,721,013 research outputs found
Ionic Hydrogenation of Azines: An Efficient Synthesis of 1,2-Dialkylhydrazines
Full text linkAn efficient synthetic method of ionic hydrogenation of azine to the corresponding 1,2-dialkylhydrazines was accomplished. Reaction time was fast and isolation and purification of the 1,2-dialkylhydrazines were operationally simple. Yields were almost quantitative for most of the products with good functional group tolerance. Moreover, the byproduct of reduction gave the opportunity for the selective synthesis, in situ, of the mono hydrazide extending the potentiality of the synthetic method described
Asymmetric Aza-Michael Reactions Catalyzed by Cinchona Alkaloids
No full textThe organocatalyzed asym. aza-Michael addn. of hydrazones to cyclic enones has been achieved in good yield and stereoselection using cheap and com. available cinchona alkaloids as catalysts. A systematic study of the influence of the structure of the enone on the stereoselectivity was carried out, leading to optically active products with up to 77% ee. The products can be recrystd. to give nearly enantiopure products, and furthermore it was shown that the products could be reduced to the corresponding 1,3-benzylidenehydrazino alc. derivs. with high diastereoselectivity
N-Acylhydrazines: Future Perspectives Offered by New Syntheses and Chemistry
No full textThis is a review of the most recent and useful synthetic methodologies for providing access to di- and trisubstituted hydrazides. New chemistry and new organometallic derivatives of the title compounds offer a new arsenal for the production of new functionalised derivatives, which are also useful as new biologically relevant molecules
Synthesis of hydrazines and hydrazides by reduction of hydrazones and azines
No full textA one-pot procedure for the synthesis of hydrazines and hydrazides involves the redn. of hydrazones RR2NN:CR1R3 or azines R2R4C:NN:CR3R5 [R-R5 = H, alkyl, aryl (at least one is other than H); or R2R4C and R3R5C are cycloaliph. or arom. rings] by Me3N.BH3. Thus, redn. of PhCH:NNMe2 with Me3N.BH3/HCl/xylene and treatment with benzoic, o-toluic, or propionic acid afforded 80-90% PhCH2N(COR)NMe2 (R = Ph, o-tolyl, or Et)
Highly enantioselective approach to geminal bisphosphonates by organocatalyzed Michael-type addition of b -ketoesters
No full textA valuable organocatalyzed protocol has been developed for the asymmetric synthesis of bisphosphonate derivatives, a class of pharmaceutically important molecules. Cheap and commercially available dihydroquinine effectively catalyzed conjugate additions of cyclic b-ketoesters to ethylidenebisphosphonate esters, leading to optically active geminal bisphosphonates, bearing an all-carbon substituted quaternary stereocenter, in high yields and enantioselectivities of up to 99% ee. Further elaborations of Michael adducts to the corresponding bisphosphonic acids or vinyl phosphonates have also been successfully performed, with conservation of optical purity
Synthesis of Chiral Chromium Tricarbonyl Labeled Thymine PNA Monomers via the Ugi Reaction
No full text(equation presented) Ugi condensation was used to synthesize the first examples of chiral racemic Ar-Cr(CO)3 labeled peptide nucleic acid (PNA) monomers bearing the organometallic moiety linked to the α-carbon of the glycine unit
Hydrazinolysis of Fischer-type oxacarbenes made efficient: a new and easy entry to alkyl and aryl hydrazinocarbene complexes
No full textHydrazinolysis of the pentacarbonyl[alkyl- or aryl-(methoxy)carbene] complexes of W0 and Cr0 with both 1,1- and 1,2-disubstituted hydrazines affords the corresponding new hydrazinocarbenes, and the presence of LiCl in the reaction medium greatly increases their yields. Thus, reaction of (OC)5W:C(OMe)Me with R2NNH2 (R2N = piperidino, morpholino, trans-2,6-dimethylmorpholino, 4-methylpiperazino) in THF gave 6-34% of the corresponding R2NNHC(Me):W(CO)5 as Z rotamers. In presence of LiCl, morpholinohydrazine afforded 72% R2NNHC(Me):W(CO)5, double the yield obtained without added LiCl
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