Development of Pd(OAc)2-catalyzed tandem oxidation of C N, C C, and C(sp3)–H bonds: Concise synthesis of 1-aroylisoquinoline, oxoaporphine, and 8-oxyprotoberberine alkaloids

Total Synthesis of the Racemate of Laurolitsine

The total synthesis of laurolitsine was achieved for the first time. This reaction was accomplished in 14 steps with a 2.3% yield (this was calculated using 3-hydroxy-4-methoxybenzaldehyde as the starting material) starting from two simple materials, 3-hydroxy-4-methoxybenzaldehyde and 2-(3-hydroxy-4-methoxyphenyl)acetic acid, and the longest linear sequence consisted of 11 steps. The key steps included an electrophilic addition reaction in which a nitro group was reduced to an amino group using lithium tetrahydroaluminum and a Pd-catalyzed direct biaryl coupling reaction. In this paper, many of the experimental steps were optimized, and an innovative postprocessing method in which 2-(3-(benzyloxy)-4-methoxyphenyl)ethanamine is salted with oxalic acid was proposed.

A unified total synthesis of benzo[d][1,3]dioxole-type benzylisoquinoline alkaloids of aporphines, coptisines, and dibenzopyrrocolines

The first total synthesis of (S)-(+)-ovigerine, (S)-(+)-N-formylovigerine, and (6aS,6a'S)-(+)-ovigeridimerine of aporphine alkaloids with a benzo[d][1,3]dioxole structure feature was established. The strategy was based upon the well-known Pd-catalyzed arylation to set the aporphine framework, and Noyori asymmetric hydrogenation followed by diastereoselective resolution to achieve excellent enantioselectivity. By slightly modifying the total synthetic route and strategically combining it with a aza-Michael addition, Bischler-Napieralski reaction and N-arylation, this methodology was also applied to the total syntheses of benzo[d][1,3]dioxole-type benzylisoquinoline alkaloids of coptisines and dibenzopyrrocolines, including two impatiens, tetrahydrocoptisine, and quaternary coptisine bromide of coptisines and two dibenzopyrrocoline analogues, with the syntheses of all of these target compounds being efficient. Among the nine synthesized compounds, the total syntheses of the three aporphines and the two impatiens, all with ee values of greater than 99%, were reported for the first time. This work also represents the first unification of synthetic routes for the total synthesis of benzo[d][1,3]dioxole-type aporphines, coptisines, and dibenzopyrrocolines.