Synthesis of benzocyclohexenes (tetrahydronaphthalenes)
Copper-catalyzed cascade reactions between alkenes or alkynes and diaryliodonium salts form carbocyclic products. The reactions proceed via arylation of the unsaturated functional group, formation of a carbocation intermediate that facilitates hydride shift pathways to translocate the positive charge to a remote position, and Friedel-Crafts-type ring formation.
F. Zhang, S. Das, A. J. Wlkinshaw, A. Casitas, M. Taylor, M. G. Suero, M. J. Gaunt, J. Am. Chem. Soc., 2014, 136, 8851-8854.
2-[(Trimethylsilyl)methyl]benzyl methanesulfonates give o-quinodimethanes in the presence of potassium fluoride and a catalytic amount of 18-crown-6 at room temperature. A subsequent reaction with electron-deficient olefins affords [4+2] cycloadducts in good yields.
H. Shirakawa, H. Sano, Synthesis, 2014, 46, 1788-1792.
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 operational simple iron(III)-catalyzed strategy toward functionalized tetrahydronaphthalenes in high yields takes advantage of a unique reactivity observed for simple aryl ketone precursors . Detailed mechanistic investigations identified pyrans as reactive intermediates that afford the desired tetrahydronaphthalenes upon iron(III)-catalyzed Friedel-Crafts alkylation.
R. B. Watson, C. S. Schindler Org. Lett., 2018, 20, 68-71.
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.
Benzyne-[2+2] cycloadditions with enamides enabled the development of a highly stereoselective tandem [2+2] cycloaddition-pericyclic ring-opening-intramolecular-N-tethered-[4+2] cycloaddition for rapid assembly of nitrogen heterocycles.
J. B. Feltenberge, R. Hayashi, Y. Tang, E. S. C. Babiash, R. P. Hsung, Org. Lett., 2009, 11, 3666-3669.