Studies on the Michael addition of naphthoquinones to sugar nitro olefins: first synthesis of polyhydroxylated hexahydro-11H-benzo[a]carbazole-5,6-diones and hexahydro-11bH-benzo[b]carbazole-6,11-diones

A Concise Total Synthesis of (+)‐Pancratistatin from D‐Glucose Featuring the Henry Reaction

“…Coincidentally, during the course of our investigations, Otero et al. also described a similar Michael addition of naphthoquinones to sugar nitroolefin E′ , thus achieving the synthesis of 2‐(benzyloxy)‐1,3,4‐trihydroxy‐1,2,4,4a,5‐hexahydro‐11b H ‐benzo[ b ]carbazole‐6,11‐dione ( D′ , Scheme ) 10. Although, the study by Otero et al.…”

“…Although the above intramolecular Henry reaction could have resulted in the formation of 12 and its three isomers, only the desired stereoisomer was obtained. In similar studies on the syntheses of various cyclitol derivatives in Henry reactions, such as those reported by Otero et al 10. and Chakraborty et al.,13 the selectivity was attributed to the stable six‐membered transition state TS‐1 (Scheme ) 10.…”

“…Although, the study by Otero et al. does not consider the bulkiness of the C3 protecting group important,10 we consider it essential from prior experience 6a. Nitroolefin E can be synthesized by the condensation of nitromethane with aldehyde F (intermolecular Henry reaction) that is derived from D ‐glucose.…”

“… The study of Otero et al. on the Michael addition of naphthoquinones to sugar nitroolefin E′ resulted in the synthesis of polyhydroxylated hexahydro‐11 H ‐benzo[ b ]carbazole‐6,11‐dione ( D′ ) 10…”

Advanced Routes in Synthesis and Reactions of Lawsone Molecules (2‐Hydroxynaphthalene‐1,4‐dione)

“…Heating lawsone 1 with 1‐methylcyclohexanecarboxylic acid in the presence of ammonium peroxysulphate in water produced 2‐hydroxy‐3‐(1‐methylcyclohexyl)naphthalen‐1,4‐dione ( 135 ) . 2‐Hydroxyl‐3‐substituted cyclohexylnaphthalen‐1,4‐dione 136 synthesized from 1 in yield 95% by heating at 90°C for 16 h with 1‐nitrocyclohexene in the presence of potassium carbonate (K 2 CO 3 ) or refluxing at 75–80°C for 3 h with 4‐(4‐chlorophenyl)‐cyclohexanecarboxylic acid in the presence of AgNO 3 in water and H 3 C–CN . Treatment of lawsone 1 with morpholine yielded 2‐hydroxy‐3‐morpholinonaphthalen‐1,4‐dione ( 137 ) (Scheme ).…”