Synthesis of isochromans
A nucleophilic substitution of alkyl fluorides was achieved in intramolecular reactions with O- and N-nucleophiles. The reaction is influenced by the nature of nucleophiles, the size of the ring to be formed, and the comformational rigidity of the precursors.
L. Zhang, W. Zhang, J. Liu, J. Hu, J. Org. Chem., 2009, 74, 2850-2853.
The use of [bis(trifluoroacetoxy)iodo]benzene as stoichiometric oxidant and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone as organocatalyst enables a convenient oxidation of isochromans. A further reaction with grignard reagents or amides affords the corresponding isochroman derivatives.
W. Muramatsu, K. Nakano, Org. Lett., 2014, 16, 2042-2045.
A transition-metal-free coupling of various triorganoindium reagents with chromene and isochroman acetals in the presence of BF3ˇOEt2 afforded 2-substituted chromenes and 1-substituted isochromans, respectively, in good yields. The reactions proceed with only 50 mol % of the organometallic, thus demonstrating the efficiency of these species.
J. M. Gil-Negrete, J. P. Sestelo, L. A. Sarandeses, Org. Lett., 2016, 18, 4316-4319.