Fluordiazadiphosphetidine, 20. Mitt. Die Dehydrofluorierung zwitterionischer und die Hydrofluorierung neutraler,hydrazinsubstituierter Fluordiazadiphosphetidine

In the presence ofEt ₃N·PF₅, F₄P^–(CH₃N)₂PF₂NHNH⁺(CH₃)₂ (I) looses one molecule of HF to yield F₃P(CH₃N)₂PF₂NHN(CH₃)₂ (II). The reaction ofI withDABCO (1,4-diazabicyclo[2.2.2]octane) yieldsDABCO·2H⁺⁺(CH₃NPF₄) ₂ ^–– (III) and [CH₃NPF₂NHN(CH₃)₂]₂ (IV). Even in the presence of CsF,II does not react with HF.

     

Experimental and theoretical FMO interaction studies of the Diels-Alder reaction of 5-acetyl-3-methythio-1,2,4-triazine with cyclic enamines

Diels-Alder reaction of 5-acetyl-3-methylthio-1,2,4-triazine with five cyclic enamines has been reinvestigated in its preparative and theoretical aspects. Its regioselectivity has been developed practically, which is in agreement with theoretical consideration of the FMO interactions, including secondary orbital interactions in the transition state. Since the energetic demands are similar for all five pairs, it has been indicated that their reactivity differences can be explained by an influence of steric hindrance in the considered transition state. In result, the synthesis of the 3-acetyl-1-methylthiocycloalka[c]pyridines, as synthons for preparation of sempervirine and its analogues has been optimized. The subsequent side reaction has been detected as a serious problem, especially in the case of the six-membered enamine, which reacts with the acetyl group of the final product formed in the reaction mixture.     

The preparation of 1,2,4-triazines from α,β-diketo-ester equivalents and their application in pyridine synthesis

The α-Chloro-α-acetoxy-β-keto-esters were prepared from β-keto-esters in good overall yields. These compounds reacted as α,β-diketo-ester equivalents with amidrazones yielding triazines, generally in good yields, or with an amidrazone and 2,5-norbornadiene in a one-pot aza Diels-Alder reaction to give the corresponding pyridines.     

Triethylammonium acetate (TEAA): a recyclable inexpensive ionic liquid promotes the chemoselective aza- and thia-Michael reactions

A new, highly efficient, inexpensive, recyclable, mild, convenient, and green protocol for chemoselective aza/thia-Michael addition reactions of amines/thiols to α,β-unsaturated compounds using triethylammonium acetate (TEAA) ionic liquid was developed. The catalyst can be recycled ten times and obviate the need for toxic and expensive catalysts. Correspondence: Akhilesh K. Verma, Green Organic Chemistry Research Laboratory, Dr. B.R. Ambedkar Center for Biomedical Research, University of Delhi, Delhi 110007, India.     

A convenient synthesis of new enantiomerically pure trihydroxypyrrolizidines using l-erythrose glycosylhydroxylamine as a masked acyclic chiral nitrone

A route has been developed for the synthesis of enantiomerically pure trihydroxylated pyrrolizidines starting from l-erythrose glycosylhydroxylamine. The latter acts as a masked acyclic nitrone and reacts diastereoselectively from its Re-face with methyl acrylate to give the corresponding isoxazolidines, which after reductive N-O cleavage are recyclized to trihydroxypyrrolizidines via a Mitsunobu condensation.     

A short microwave-assisted synthesis of tetrahydroisoquinolin-pyrrolopyridinones by a triple process: Ugi-3CR-aza Diels-Alder/S-oxidation/Pummerer

A series of tetrahydroisoquinolin-pyrrolopyridinones were prepared from an easily accessible aldehyde, a commercially available amine, a readily isolable isonitrile, and maleic anhydride via a triple process: Ugi-3CR-aza Diels-Alder/S-oxidation/Pummerer. The combination of a multicomponent Ugi-type reaction with other post-functionalization processes provides a powerful tool for the preparation of fused polyheterocyclic compounds.     

A convenient synthesis of substituted 2,2′:6′,2″-terpyridines

The 2,2′:6′,2″-terpyridines 8a and 8b were prepared in good yield by reacting α-acetoxy-α-chloro-β-keto-esters 1 (R¹ = ⁿPr and Ph) with the bis-amidrazone 7 and 2,5-norbornadiene 5 in ethanol at reflux.