Synthesis of 9-Fluorenylidenes and 9,10-Phenanthrenes through Palladium-Catalyzed Aryne Annulation by o-Halostyrenes and o-Halo Allylic Benzenes

Abstract

A number of functionally substituted 9-fluorenylidenes and 9,10-phenanthrenes have been synthesized from substituted ortho-halostyrenes and ortho-halo allylic benzenes respectively in good yields by the palladium-catalyzed annulation of arynes. The methodology tolerates a variety of functional groups, including cyano, ester, aldehyde and ketone groups, occurs under relatively mild reaction conditions, and involves the generation of two new carbon-carbon bonds, thus providing these important carbocyclic ring systems in a single synthetic step.

Silicon‐Induced Phenanthrene Formation from Benzynes and Allenylsilanes

“…Four advantages are associated with this newly invented reaction: 1) The starting materials were versatile; benzynes and allenylsilanes with various substituents and ligands were adaptable to generation of the desired products; 2) (α‐Phenanthrenyl)vinylsilanes were produced exclusively as the E ‐isomers; often the methods for the generation of vinylsilanes lead to a mixture of E ‐ and Z ‐isomers;33, 34 3) No catalysts were required in our reaction for the phenanthrenes formation; other examples usually need catalysts such as CuBr 2 ,35 CuI,36 NiBr 2 (dppe),3 and Pd with various ligands;37, 38 4) The new reaction provided products in good yields (66–92 %), which were higher than those associated with the metal‐catalyzed3, 39 cyclizations in the formation of phenanthrenes from benzynes and (norsilyl)allenes (29–77 %).…”

Benzoic Acid‐Promoted Intermolecular [3+2] Cycloaddition with Air as the Terminal Oxidant: General Approach toward Pyrrolo[2, 1‐a]isoquinolines

“…The intriguing biological activities of these compounds have attracted considerable interest from synthetic chemists regarded the development of new methods for the efficient construction of pyrrolo[2, 1‐ a ]isoquinolines . During the past three decades, several approaches have been developed for the synthesis of pyrrolo[2, 1‐ a ]isoquinolines, including dipolar and azadiene Diels‐Alder cycloadditions, oxidative dimerization, and double‐barreled Heck cyclization reactions . However, the application of these methods has been restricted by their limited substrate scope or their requirement for multiple synthetic steps.…”

Reactions of Arynes Involving Transition-Metal Catalysis

“…Arylnaphthalene lignans occur widely in nature and exhibit various biological activities. Taiwanin C (25) and E (26) are two representative natural products containing arylnaphthalene liganan moieties. Sato, Mori, and Tamura reported the total syntheses of taiwanin C (25) and E (26) by using a [2+2+2] cocyclization involving an aryne as the key step (Scheme 8).…”

“…Taiwanin C (25) and E (26) are two representative natural products containing arylnaphthalene liganan moieties. Sato, Mori, and Tamura reported the total syntheses of taiwanin C (25) and E (26) by using a [2+2+2] cocyclization involving an aryne as the key step (Scheme 8). 12 Aryne precursor 21 reacted with the prepared diyne 22 to form the scaffold of taiwanin C (25) and E (26) in 61% yield.…”

“…Sato, Mori, and Tamura reported the total syntheses of taiwanin C (25) and E (26) by using a [2+2+2] cocyclization involving an aryne as the key step (Scheme 8). 12 Aryne precursor 21 reacted with the prepared diyne 22 to form the scaffold of taiwanin C (25) and E (26) in 61% yield. A key intermediate 24 was afforded in four steps after functional group transformations.…”