Catalyst-Free Rearrangement of Allenyl Aryldiazoacetates into 1,5-Dihydro-4H-pyrazol-4-ones.
Phenylpropargyl diazoacetates exist in equilibrium with 1-phenyl-1,2-dien-1-yl diazoacetate - allenes that are rapidly formed at room temperature through 1,3-acyloxy migration catalyzed by gold(I) or gold(III) compounds, and these catalysts react solely with the π-donor rather than with the diazo group. The product allene of the aryldiazoacetates undergoes rearrangement that is not catalyzed by gold in which the terminal nitrogen of the diazo functional group adds to the central carbon of the allene, initiating a sequence of bond-forming reactions, resulting in the production of 1,5-dihydro-4H-pyrazol-4-ones in good yields. These 1,5-dihydro-4H-pyrazol-4-ones undergo intramolecular 1,3-acyl migration to form an equilibrium mixture and can quantitatively transfer the acyl group to an external nucleophile with formation of 4-hydroxypyrazoles. Reactions of phenylpropargyl phenyldiazoacetates catalyzed by cationic gold complexes are initiated at the diazo functional group to form a gold carbene whose subsequent cascade process (intramolecular addition, then aromatic substitution) results in the formation of a product that is uniquely characteristic of this pathway.
Department of Chemistry, The University of Texas at San Antonio , San Antonio, Texas 78249, United States.
Kostiantyn O
KO
Marichev
Department of Chemistry, The University of Texas at San Antonio , San Antonio, Texas 78249, United States.
Huang
H
Qiu
Department of Chemistry, The University of Texas at San Antonio , San Antonio, Texas 78249, United States.
Austin C
AC
Offield
Department of Chemistry, The University of Texas at San Antonio , San Antonio, Texas 78249, United States.
Hadi
H
Arman
Department of Chemistry, The University of Texas at San Antonio , San Antonio, Texas 78249, United States.
Michael P
MP
Doyle
D000085:Acetates / Q000737:chemistry*; D000466:Alkadienes / Q000737:chemistry*; D002384:Catalysis; D003979:Diazonium Compounds / Q000737:chemistry*; D015394:Molecular Structure; D011720:Pyrazoles / Q000737:chemistry*; D013237:Stereoisomerism
D000085:Acetates; D000466:Alkadienes; D003979:Diazonium Compounds; D011720:Pyrazoles; C025947:propadiene