The thermal cyclization of 3,4-diphenylbuta-1,3-dienyl isocyanates 1, generated in situ from the corresponding azides, was investigated using iodine as a catalyst. Diphenylpyridinones 2, phenylnaphthalenes 3, and indenes 4 were produced via intramolecular ring closure. The nature of the substituents on the phenyl rings was found to be crucial to the distribution of cyclized products 2-4. The mechanism of the reaction is also discussed.

A series of A/D-ring substituted dibenzo[de,g]quinolin-7-ones was produced from the corresponding isoquinolinones and (2-bromophenyl)acetonitriles in four steps. This represents a convenient approach toward the synthesis of tetracyclic alkaloids. A direct conversion of 1-(2-bromobenzoyl)isoquinolines to dibenzo[de,g]quinolin-7-ones is the key step in the total synthesis. The yield of the reductive photocyclization depends on the position of the substituents at the isoquinolyl ring and the phenyl group. The mechanism of the reductive photocyclization is also discussed.

Phenanthroindolizidines and phenanthroquinolizidines were concisely synthesized by the reductive decyanization of cyano-promoted intramolecular aza-Diels-Alder cycloadducts followed by aryl-aryl coupling. Cyano groups were removed from α-aminoacrylonitriles via treatment with sodium borohydride in 2-propanol in almost quantitative yields; a possible mechanism was proposed and examined using D-labeling experiments. A systematic study of the effects of the phenanthrene substitution pattern on the anticancer activity against three human cancer cell lines was discussed.

Org. Lett. 18 (2016) 4, 638-641, http://dx.doi.org/10.1021/acs.orglett.5b03395 ; Sch. Pharm., China Med. Univ., Taichung 40402, Taiwan; Eng.) -M. Tismer

Direct Conversion of 1-(2-Bromobenzoyl)isoquinolines to Dibenzo[de,g]quinolin--7-ones via Reductive Photocyclization. -A convenient and new one-pot method for the synthesis of tetracyclic alkaloids is presented via reductive photocyclization. The yields are enhanced when -O-Me is at the 5-or 7-position of the isoquinolyl ring or -CF3 at the 5-position of the phenyl group.