Hydroarylation of Alkynes with Phenols in the Presence of Gallium Complexes of a Labile N‐Ligand: Synthesis of Chromenes

Abstract

In the presence of (dpp‐bian)Ga–Ga(dpp‐bian) (1) and [dpp‐bian(Ph)C=C(H)]Ga–Ga[(H)C=C(Ph)dpp‐bian] (2) {dpp‐bian = 1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene}, phenylacetylene reacts with 1‐naphthol to give 2‐(1‐phenylvinyl)naphthalen‐1‐ol (3). In solution in the presence of complexes 1 or 2, compound 3 undergoes further dimerization to give 2‐[4‐methyl‐2,4‐diphenyl‐3,4‐dihydro‐2H‐benzo[h]chromen‐2‐yl]naphthalen‐1‐ol (C36H28O2), whose diastereomers 4 and 5 were isolated in crystalline form. Diastereomer 4 is the kinetically favored product, which, however, undergoes conversion into diastereomer 5 in solution at elevated temperature. The structures of 4 and 5 were determined by single‐crystal X‐ray analysis. The catalytic activity of complexes 1 and 2 in the hydroarylation reactions of phenylacetylene and some other alkynes with different arenes has been investigated. By the reaction of phenylacetylene with 3,5‐di‐tert‐butylphenol, 5,7‐di‐tert‐butyl‐4‐methyl‐2,4‐diphenyl‐4H‐chromene (7) has been prepared for the first time.

Indium triflate catalyzed microwave-assisted alkenylation of methoxyphenols: synthesis of indenes and chromenes

“…The formation of chromene derivatives by alkenylation of phenol is consistent with the recent report by the Fedushkin group that appeared during the preparation of this manuscript. 9 Based on literature reports and our previous results, it is believed that the reaction proceeds through alkenylation of phenol to give (1-arylvinyl)phenol 3, which further undergoes second alkenylation and cycloisomerization to give indene in the case of 4-methoxyphenol. It is believed that due to the blocked C-3 position in the alkenylated product from 3-methoxyphenol, second alkenylation may be occurring at the vinylic position, and further cyclization leads to the formation of 5.…”

“…[1][2][3][4] In particular, alkenylation of phenols with alkynes has been reported using SnCl 4 , 5 GaCl 3 , 6 nanoporous FeAl-KIT-5, 7 Pd 2 (dba) 3 8 and gallium complexes of labile N-ligands. 9 We have previously demonstrated that indium triflate [In(OTf ) 3 ] is an efficient catalyst for alkenylation of phenols using alkynes under microwave irradiation and the generated ortho-vinyl at phenols can be used for the synthesis of 1,2-diarylnaphtho[2,1-b]furans. 10 Indene ring frameworks are present in many natural products and bioactive pharmaceutical compounds.…”

Element‐Ligand Cooperativity with p‐Block Elements

“…However, since no formation of cycloadducts of 62 with carbodiimides was observed, no clear evidence for GaLC was provided . The hydroarylation of phenylacetylene with 2‐naphthol also proceeded in the presence of catalytic amounts of 62 (Figure e) , . Phenols or internal alkynes were not suitable for this procedure and did not yield the desired compounds.…”

Low-Coordinate Mixed Ligand NacNac Complexes of Rare Earth Metals

“…BIAN dipp , 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene, is a redox-active diimine ligand possessing the conformational rigidity of the diimine moiety and pronounced steric hindrances around nitrogen atoms. The unique reactivity of the main-group metal complexes with BIAN dipp ligand was shown by Fedushkin et al in the examples of addition (in some cases, reversible) and activation of substituted alkynes, alkenes [ 33 , 34 , 35 , 36 , 37 , 38 ]. It would be very interesting to combine sterically hindered NacNac ligands with redox-active sterically hindered o-iminobenzoquinones and bis-iminoacenaphthenes in a coordination sphere of rare earth.…”