Highly Efficient Gold‐Catalyzed Synthesis of Dibenzocycloheptatrienes

Abstract

Dibenzocycloheptatrienes are obtained by a gold-catalyzed 7-exo-dig hydroarylation protocol in a highly efficient manner. The gold-catalyzed reaction usually gives the products in high yields and excellent selectivity. This procedure provides an easy and efficient access to dibenzocycloheptanoids, which are an interesting and unique class of natural products. This was underlined by the first total synthesis of reticuol.

Gold(I)-Catalyzed Activation of Alkynes for the Construction of Molecular Complexity

“… 367 Dibenzocycloheptatrienes were obtained by a related transformation through a 7- exo -dig hydroarylation. 368 …”

Anatomy of gold catalysts: facts and myths

“…31 Although less commonly employed, these complexes proved to be far superior to phosphine and NHC-derived gold catalysts for the activation of the less reactive substrates and for enhancing the carbocationic character of the reactive inter-mediates in the addition of C-nucleophiles of 1,6-enynes 32 and in other processes. [33][34][35][36][37] Other related highly electrophilic complexes have also been developed. 38,39 A variety of chiral mono-and dinuclear phosphine, phosphite, and phosphoramidite gold complexes 26-34 have been developed for the enantioselective activation of alkynes and allenes (Fig.…”

Mechanistic Insights into the Post‐Cyclization Isomerization in Gold‐Catalyzed 7‐exo‐dig‐Hydroarylations

“…After 24 hours, complete conversion was achieved giving a mixture of 2 a and 3 a in 99 % yield, determined by NMR spectroscopy, and a selectivity for 3 a of 8:1. In contrast to this result, the same reaction at room temperature without the additive gave 2 a as major product (Scheme ) 8…”

“…In our recent report on the synthesis of dibenzocycloheptatrienes,8 we found that for many catalyst systems and especially low‐catalyst loadings, a mixture of the primary 3 a and the rearranged product 2 a was obtained. Interestingly, 3 a was stable at ambient conditions and the obtained ratio 2 a / 3 a did not change by dissolution in CDCl 3 or during performance of column chromatography with silica gel.…”

“…In contrast to this result, the same reactiona t room temperature withoutt he additive gave 2a as major product (Scheme 3). [8]…”