Gold(I)-Catalyzed Formation of Naphthalene/Acenaphthene Heterocyclic Acetals

Abstract

A gold-catalyzed addition/cyclization reaction to form 3-alkoxy-benzo[de]isochromene derivatives was developed. All reactions, performed in mild conditions, exhibited high regioselectivity and good to excellent reaction yields. Additionally, optimized methodology was used in total synthesis of 2-phenylphenalenone, an alleged natural product found in Macropidia fuliginosa plant.

Optimizing Catalyst and Reaction Conditions in Gold(I) Catalysis–Ligand Development

“…The reaction was further optimized in the presence of various alcohols to obtain 3-alkoxy-benzo[de]isochromene derivatives. 105 IPr Cl (NHC-8), with Cl atoms in the backbone, shows a very similar %V bur to that of IPr (44.9 30,106 vs 45.4 30 ); however, as expected due to the electron withdrawing effect of the Cl atoms, IPr Cl (NHC-8) is less electron-donating than IPr (TEP = 2055.1 vs 2051.5 cm −1 , respectively). 21 This modification has proven to be beneficial for a handful of catalytic transformations.…”

“…Among the NHC ligands tested (IPr, NHC-1 ; SIPr, NHC-2 ; and NQ-IPr, NHC-9 ), all in the form of [Au­(NHC)­(NTf 2 )] complexes, SIPr showed a higher selectivity toward species B (Scheme ). The reaction was further optimized in the presence of various alcohols to obtain 3-alkoxy-benzo­[de]­isochromene derivatives …”

Synthesis of Perinaphthenones via BF3.Et2O Mediated One‐Pot Cascade 4,5‐Annulation Reactions of 1‐Naphthols and Ynones

“…Yield: 54.3 mg (30%); R f = 0.4 (EtOAc:hexane = 1:4); Dark yellow solid; Melting point 87.3-89°C; 1 H-NMR (400 MHz, CDCl 3 ): δ 8.73 (dd, J = 1. 18,7.38 Hz,1H),8.34 (dd,J = 1.18,8.34 Hz,1H),7.89 (d,J = 10.08 Hz,1H),7.75 (dd,J = 7.50,8.14 Hz,1H),7.55 (s,1H),4H),3H),7.07 (d,J = 8.64 Hz,2H),6.71 (d,J = 10.12 Hz, 1H), 3.91 (s, 3H); 13 C-NMR (100 MHz, CDCl 3 ): δ 185. 5,159.8,144.6,144.4,140.0,139.2,133.7,131.5,131.5,130.9,130.4,130.4,130.1,130.1,128.6,128.5,128.3,128.2,126.8,123.5,114.0,55.5;HRMS(EI) 7,144.9,144.7,140.3,139.4,138.4,136.3,133.8,131.0,130.6,130.5,130.4,130.3,…”

“…Next, Yavari group reported the synthesis of highly functional perinaphthenones in the presence of triphenylphosphine from acetylenic ester and acenaphthoquinone‐malononitrile adduct (Scheme 1, Equation c) [17] . In addition to these, Michalska and his coworkers developed methodology for the synthesis of 3‐alkoxy‐benzo[de]isochromene derivatives through gold catalysis, which was further converted into phenylperinaphthenone derivative by the treatment with PTSA [18] . Although, the reported methods are useful for accessing diverse phenylperinaphthenones, they are associated with one or more shortcoming such as low yields, use of expensive metal catalyst, the use of complex starting materials.…”

“…[17] In addition to these, Michalska and his coworkers developed methodology for the synthesis of 3-alkoxybenzo [de]isochromene derivatives through gold catalysis, which was further converted into phenylperinaphthenone derivative by the treatment with PTSA. [18] Although, the reported methods are useful for accessing diverse phenylperinaphthenones, they are associated with one or more shortcoming such as low yields, use of expensive metal catalyst, the use of complex starting materials. Hence, the synthesis of phenylperinaphthenones derivative from easily available starting material under mild condition is highly desirable.…”