Stereochemistry of 1,3-Dipolar Cycloadditions of Nitrones with (E)-1-Alkyl-2-nitroethenes.
نویسندگان
چکیده
منابع مشابه
Highly enantioselective catalytic 1,3-dipolar cycloadditions of α-alkyl diazoacetates: efficient synthesis of functionalized 2-pyrazolines.
Highly enantioselective 1,3-dipolar cycloaddition reactions of α-substituted diazoacetates are accomplished by catalysis of the chiral oxazaborolidinium ion. Functionalized 2-pyrazolines are synthesized in high to excellent enantiomeric ratios (up to >99 : 1). The synthetic utility of 2-pyrazoline was expanded via preparation of 2,4-diamino ester compounds bearing a chiral quaternary carbon cen...
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Strain-promoted cycloadditions of nitrones with cyclooctynes (k(2) = 1.5 M(-1) s(-1) at 25 degrees C) are up to 25 times more rapid than comparable reactions of azides.
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ABSTRACT The electrophilicity of (E)-2-aryl-1-cyano-1-nitroethenes is not sufficient to induce a zwitterionic course of their [4+2] cycloaddition to cyclopentadiene. The one-step mechanism of these reactions is indicated by the activation parameters, and the substituent and solvent effects on the reaction. GRAPHICAL ABSTRACT
متن کاملKinetics studies of rapid strain-promoted [3 + 2]-cycloadditions of nitrones with biaryl-aza-cyclooctynone.
Strain-promoted cycloadditions of cyclic nitrones with biaryl-aza-cyclooctynone (BARAC) proceed with rate constants up to 47.3 M(-1) s(-1), this corresponds to a 47-fold rate enhancement relative to reaction of BARAC with benzyl azide and a 14-fold enhancement over previously reported strain promoted alkyne-nitrone cycloadditions (SPANC). Studies of the SPANC reaction using the linear free ener...
متن کاملIridium–catalyzed 1,3–dipolar cycloadditions
1,3–Dipolar cycloaddition reactions (DCR) are atom–economic processes that permit the construction of heterocycles. Their enantioselective versions allow for the creation of up to four adjacent chiral centers in a concerted fashion. In particular, well–defined half–sandwich iridium (III) catalysts have been applied to the DCR between enals or methacrylonitrile with nitrones. Excellent yield and...
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ژورنال
عنوان ژورنال: Chemical and Pharmaceutical Bulletin
سال: 1992
ISSN: 0009-2363,1347-5223
DOI: 10.1248/cpb.40.2014