One-step route to tricyclic fused 1,2,3,4-tetrahydroisoquinoline systems via the Castagnoli–Cushman protocol

• Aleksandar Pashev,
• Nikola Burdzhiev and
• Elena Stanoeva

Beilstein J. Org. Chem. 2020, 16, 1456–1464, doi:10.3762/bjoc.16.121

• . Keywords: benzo[a]quinolizidinones; Castagnoli–Cushman reaction; 3,4-dihydroisoquinolines; monocyclic anhydrides; pyrrolo[2,1-a]isoquinolinones; Introduction The benzo[a]quinolizidine ring system is an important heterocyclic framework found in natural products and prospective pharmaceuticals [1]. This

• ], there are only few reports featuring reactions between monocyclic anhydrides 5–9 and cyclic imines 12 in the literature [12][25][26][27][28][29]. Thus, it was shown that glutaconic anhydride reacts with 1-methyl-3,4-dihydroisoquinoline and with 1-chloroisoquinoline to give 11b-methylbenzo[a]quinolizin-4

• expected fused δ-lactams [26]. The purpose of the present investigation was to explore the much less studied reaction between monocyclic anhydrides 5–8 and cyclic imines (such as 6,7-dimethoxy-3,4-dihydroisoquinoline (18) and its 1-alkyl derivatives 19 and 20) as a potential one-step route towards