Synthesis of Spiro Polycyclic Aromatic Hydrocarbons by Intramolecular Palladium-Catalyzed Arylation

Abstract

The palladium-catalyzed intramolecular arylation reaction has been applied to the synthesis of the spiro polycyclic aromatic hydrocarbons and planar polycyclic aromatic hydrocarbons by formation of a six-membered ring. The reaction proceeds more readily with aryl bromides substituted with electron-withdrawing groups by using palladium acetate in N,N-dimethylformamide as the solvent. For the less reactive p-methoxyaryl derivatives the use of LiI as an additive was shown to give the best results. The results obtained in the cyclization of nitro derivatives 21 and 23 suggest that the second step of the cyclization reaction is not an electrophilic substitution reaction.

Application of a catalytic palladium biaryl synthesis reaction, via C–H functionalization, to the total synthesis of Amaryllidaceae alkaloids

“…35 However, such substituent effects have been called into question. 36 The third scenario is that an h 2 -arene (or an h 1 -arene) aryl-Pd complex precedes an agostic interaction between the palladium and the carbon-hydrogen bond. 37 An agostic effect may possibly represent a transition state for C-H activation which ultimately results in the formation of the cisdiarylpalladium (II) species.…”

“…37 An agostic effect may possibly represent a transition state for C-H activation which ultimately results in the formation of the cisdiarylpalladium (II) species. 33,36,38 The dioxolane products 7(a, b and d) were hydrolyzed in refluxing 50% aqueous 6 N HCl/THF for 5 h. Evaporation of the THF resulted in the precipitation of the dark red/ purple compounds 8 in greater than 85% yield. Rigby and Mateo reported an alternative method for what was claimed to be the synthesis of compound 8b.…”

syn-Trialkylated Truxenes: Building Blocks That Self-Associate by Arene Stacking

“…[17] Interestingly, by using Pd(OAc) 2 as the catalyst syn-3 b cyclized more readily (DMF, 130 8C, 24 h) than its isomer 2 b (DMF or DMA, 36 h, 150 ± 165 8C) to give 6 in good yields (71 ± 79 %). [17] Interestingly, by using Pd(OAc) 2 as the catalyst syn-3 b cyclized more readily (DMF, 130 8C, 24 h) than its isomer 2 b (DMF or DMA, 36 h, 150 ± 165 8C) to give 6 in good yields (71 ± 79 %).…”

Palladium-Catalyzed IntramolecularArylation Reaction: Mechanism and Application for theSynthesis of Polyarenes

“…25 The palladium-catalyzed cyclization of 15 proceeded under the standard conditions (140°C, 36 h) to give 16 in 80% yield. …”

“…25 However, the cyclization of methoxy derivative 10b was very sluggish under these conditions. Replacing Bu 4 NBr with LiI (2.5 equiv) led to 11b in 50% yield (130°C, 4 d).…”