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Ring-Expansion

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The reaction of β-keto esters with CF3CO2ZnCH2I provided the corresponding chain-extended products in moderate to good yields. α-Substituted acyclic β-keto esters reacted less efficiently than cyclic β-keto esters or simple β-keto esters.
S. Xue, Y.-K. Liu, L.-Z. Li, Q.-X. Guo, J. Org. Chem., 2005, 70, 8245-8247.


The homologation of arylcyclobutanones with trimethylsilyldiazomethane gives enolsilanes in the presence of Sc(OTf)3 as catalyst with a high preference for methylene migration, whereas Sc(hfac)3 leads to β-ketosilanes. Each adduct affords the cyclopentanone upon hydrolysis.
J. A. Dabrowski, D. C. Moebius, A. J. Wommack, A. F. Kornahrens, J. S. Kingsbury, Org. Lett., 2010, 12, 3598-3601.


Functionalized α-tertiary and -quaternary 2-arylcycloalkanones are rapidly accessed by scandium(III) triflate-catalyzed diazoalkane-carbonyl homologations. Pairing readily available bis- and tris(oxazoline) based ligands with scandium triflate allows access to arylated medium ring carbocycles with high enantioselectivities and excellent yield.
V. L. Rendina, H. Z. Kaplan, J. S. Kingsbury, Synthesis, 2012, 44, 686-693.


V. L. Rendina, H. Z. Kaplan, J. S. Kingsbury, Synthesis, 2012, 44, 686-693.


A stereospecific gold(I)-catalyzed rearrangement of 1-alkynyl cyclobutanols and cyclopropanols provides alkylidene cycloalkanones. The reaction tolerates terminal alkynes as well as alkyl, aryl, and halo-substitution at the acetylenic position and substituents on the ring.
J. P. Markham, S. T. Staben, F. D. Toste, J. Am. Chem. Soc., 2005, 127, 9708-9709.


Oxidative ring expansion of methylenecyclopropanes with CAN under oxygen atmosphere was investigated. A facile conversion affording 2,2-diarylcyclobutanones occurred in good yields.
V. Nair, T. D. Suja, K. Mohanan, Synthesis, 2006, 2531-2534.


[ReBr(CO)3(thf)]2 catalyzes the reaction of a 1,3-dicarbonyl cyclic compound with an acetylene to give a medium-sized cyclic compound in excellent yield. By using isocyanide as an additive, the insertion of acetylenes into a carbon-carbon single bond occurs under mild conditions.
Y. Kuninobu, A. Kawata, K. Takai, J. Am. Chem. Soc., 2006, 128, 11368-11369.