Synthesis of indanes
A number of indenes have been prepared in good yields by treatment of o-bromobenzyl zinc bromide with various terminal and internal alkynes in the presence of a nickel catalyst. The nickel-catalyzed carboannulation reaction was successfully extended to the synthesis of indanes using acrylates and styrene instead of an alkyne.
R. Deng, L. Sun, Z. Li, Org. Lett., 2007, 9, 5207-5210.
An intramolecular, Pd-catalyzed C-H alkylation of arenes and heteroarenes is successful with various unactivated primary and secondary alkyl halides, including those with β-hydrogens. The mild, catalytic reaction conditions are highly functional group tolerant and facilitate access to a broad range of synthetically and medicinally interesting carbocyclic and heterocyclic systems.
A. R. O. Venning, P. T. Bohan, E. J. Alexanian, J. Am. Chem. Soc., 2015, 137, 3731-3734.
An asymmetric Ni-catalyzed intramolecular reductive Heck reaction of unactivated alkenes tethered to aryl bromides provides various benzene-fused cyclic compounds bearing a quaternary stereogenic center in good to excellent yields and high enantioselectivities. A mechanism involves an enantiodetermining migratory insertion and a subsequent protonation with water or alcoholic solvents.
F. Yang, Y. Jin, C. Wang, Org. Lett., 2019, 21, 6909-6913.
A highly enantioselective, intramolecular arylcyanation of unactivated olefins via C-CN bond activation has been accomplished using a Ni(0) catalyst, BPh3 as co-catalyst, and TangPHOS as a chiral ligand. Two new C-C bonds and one quaternary carbon stereogenic center are generated in a single synthetic step, converting readily available benzonitriles into 1,1-disubstituted indanes in good yield.
M. P. Watson, E. N. Jacobsen, J. Am. Chem. Soc., 2008, 130, 12594-12595.
An enantioselective nickel-catalyzed Negishi cross-coupling of racemic secondary benzylic bromides and chlorides is described. The catalyst components are commercially available and air-stable, and the reaction is not highly oxygen- or moisture-sensitive.
F. O. Arp, G. C. Fu, J. Am. Chem. Soc., 2005, 127, 10482-10483.
A mild and convenient free-radical cyclization of organohalides in the presence of a NiCl2 • DME/Pybox complex as the catalyst and zinc powder in methanol efficiently gives carbo-, oxa-, and azacycles as products in high yields from unsaturated alkyl halides.
H. Kim, C. Lee, Org. Lett., 2011, 13, 2050-2053.
A Pd-catalyzed C(sp3)-H functionalization/carbenoid insertion enables the rapid synthesis of bicyclic frameworks, generating all-carbon quaternary centers via multiple C-C bond formations in a straightforward manner.
Á. Gutiérrez-Bonet, F. Juliá-Hernández, B. de Luis, R. Martin, J. Am. Chem. Soc., 2016, 138, 6384-6387.
A stereoselective sequence of a RhI-catalyzed conjugate addition of boronic acids to enones followed by a Michael cyclization gives 1,2,3-trisubstituted indans in a highly regio- and stereoselective fashion.
C. Navarro, A. G. Csák˙, Org. Lett., 2008, 10, 217-219.
A cationic rhodium(I)/BINAP complex-catalyzed decarboxylative [2 + 2 + 2] cycloaddition of 1,6- and 1,7-diynes with commercially available vinylene carbonate enables a new route to substituted phenols.
H. Hara, M. Hirano, K. Tanaka, Org. Lett., 2009, 11, 1337-1340.
A AuCl-catalyzed, flexible synthesis of highly substituted, benzyl-protected phenols unites enal/enones and benzyl allenyl ethers in a [3+3] fashion in two steps, allowing excellent control of substitution at the benzene ring.
X. Huang, L. Zhang, Org. Lett., 2007, 9, 4627-4630.