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Synthesis of isoquinolines

Recent Literature

Reaction of N-carbamoyl-functionalized enamine derivatives with benzyne affords substituted indolines. An orthogonal reactivity is uncovered when related enamine derivatives are modified as amides, such that isoquinolines are formed as the product of condensation with benzyne.
C. D. Gilmore, K. M. Allan, B. M. Stoltz, J. Am. Chem. Soc., 2008, 130, 1558-1559.

CuI-catalyzed coupling of 2-halobenzylamines with β-keto esters or 1,3-diketones in i-PrOH in the presence of of K₂CO₃ produced 1,2-dihydroisoquinolines as the cyclization products, which underwent smooth dehydrogenation under air atmosphere to afford substituted isoquinolines.
B. Wang, B. Lu, Y. Jiang, Y. Zhang, D. Ma, Org. Lett., 2008, 10, 2761-2763.

α-Azido carbonyl compounds bearing a 2-alkenylaryl moiety at the α-position are promising precursors for synthesis of isoindole and isoquinoline derivatives via 1,3-dipolar cycloaddition of azides onto alkenes and 6π-electrocyclization of N-H imine intermediates, respectively.
B. W.-Q. Hui, S. Chiba, Org. Lett., 2009, 11, 729-732.

Ag-catalyzed cyclization of 2-alkynyl benzyl azides offers an efficient method for the synthesis of substituted isoquinolines. The reaction proceeds smoothly in good yields and tolerates various functional groups.
Y.-N. Niu, Z.-Y. Yan, G.-L. Gao, H.-L. Wang, X.-Z. Shu, K-G. Ji, Y.-M. Liang, J. Org. Chem., 2009, 74, 2893-2896.

The reaction of 2-alkynyl-1-methylene azide aromatics with iodium donors gave 1,3-disubstituted 4-iodoisoquinolines in good yields. Electron-donating and withdrawing substituents on the aromatic ring were equally tolerated. At the alkyne terminus, electron-neutral or donating substituents are clearly favored. A short synthesis of norchelerythrine is described.
D. Fischer, H. Tomeba, N. K. Pahadi, N. T. Patil, Z. Huo, Y. Yamamoto, J. Am. Chem. Soc., 2008, 130, 15720-15725.

Readily available 2-azido-3-arylacrylates react with α-diazocarbonyl compounds and triphenylphosphine to furnish isoquinolines in good yields. The efficient and general procedure involves a Wolff rearrangement, an aza-Wittig reaction, and an electrocyclic ring closure.
Y.-Y. Yang, W.-G. Shou, Z.-B. Chen, D. Hong, Y.-G. Wang, J. Org. Chem., 2008, 73, 3928-3930.

The direct conversion of various amides to isoquinoline and β-carboline derivatives via mild electrophilic amide activation, with trifluoromethanesulfonic anhydride in the presence of 2-chloropyridine followed by cyclodehydration upon warming provides the desired products with short overall reaction times.
M. Movassaghi, M. D. Hill, Org. Lett., 2008, 10, 3485-3488.