Novel Synthesis of Isoquinolines Using Isobenzofuran−Nitrile Diels−Alder Reactions

[reaction: see text] The synthesis of isoquinolines through coupling of 2-alkynylbenzaldehyde derivatives with beta-cyanocarbene complexes has been examined. The reaction involves formation of an isobenzofuran followed by intramolecular Diels-Alder reaction with the nitrile, a process with limited precedent. The unique success of this process in this system has been attributed to deoxygenation of the initial adduct to form the isoquinoline ring system.