Copper-catalyzed arylstannylation of arynes in a sequence

Abstract

Diverse ortho-stannylbiaryls and teraryls have been synthesized by copper-catalyzed arylstannylation of arynes, in which the single or dual insertion of arynes into arylstannanes is precisely controllable by simply changing the equivalence of the aryne precursors employed.

”Copper Effect” in Migita–Kosugi–Stille Coupling Revisited

“…We previously reported on the copper-catalyzed arylstannylation of arynes in DEE, where arylstannanes of higher tin-Lewis acidity reacted faster via Sn/Cu transmetalation as a key step, and moreover tributyl(pentafluorophenyl)stannane (1a) actually underwent the stoichiometric transmetalation with CuTC. 23 These results in conjunction with the distinct difference in the reactivity between 1a and 1f in the present Pd/Cu-cocatalyzed MKSC imply that the transmetalation-based "copper effect" would be operative even in less polar ethereal solvents, being in stark contrast to the conventional notion of the copper behavior in MKSC. Then, our attention was focused on correlation between MKSC (≈ transmetalation) reactivity and tin-Lewis acidity, which was found to be estimated by the 119 Sn NMR chemical shift.…”

“…Then, our attention was focused on correlation between MKSC (≈ transmetalation) reactivity and tin-Lewis acidity, which was found to be estimated by the 119 Sn NMR chemical shift. 23,38 The 119 Sn NMR method worked well for the prediction of the reactivity toward the arylstannylation, and also electrophilicity has been generally determined by NMR chemical shift. 39 However, we needed additional method of determining tin-Lewis acidity, because the NMR evaluation sometimes mislead; Brønsted acidity of fluoroaromatic compounds does not correspond to 1 H NMR chemical shift ( 1 H NMR: C6H6, 7.41 ppm > C6F5H, 6.91 ppm vs. pKa: C6H6 40,41 > C6F5H 41,42 ), and degree of shielding effect in 1 H NMR was reported to be different between a fluoroaromatic and a benzene ring, which might be the case in 119 Sn NMR.…”

“…14,22 On the other hand, we have recently reported on copper-catalyzed arylstannylation of arynes, which proceeds via the Sn/Cu transmetalation in an ethereal solvent, 1,2-diethoxyethane (DEE). [23][24][25] This result in conjunction with advantages of ethereal solvents (e.g., unique media in cross-coupling reactions; 26 environmentally friendly characteristics as represented by biomass-derived 2-MeTHF; 27 suitability for cross-coupling-based polymer syntheses 28 ) motivated us to explore fully the Pd/Cu-cocatalyzed MKSC in ethereal solvents without preconceived ideas.…”

”Copper Effect” in Migita–Kosugi–Stille Coupling Revisited

“…Then, our attention was focused on correlation between MKSC (≈ transmetalation) reactivity and tin-Lewis acidity, which was found to be estimated by the 119 Sn NMR chemical shift. 23,38 The 119 Sn NMR method worked well for the prediction of the reactivity toward the arylstannylation, and also electrophilicity has been generally determined by NMR chemical shift. 39 However, we needed additional method of determining tin-Lewis acidity, because the NMR evaluation sometimes mislead; Brønsted acidity of fluoroaromatic compounds does not correspond to 1 H NMR chemical shift ( 1 H NMR: C6H6, 7.41 ppm > C6F5H, 6.91 ppm vs. pKa: C6H6 40,41 > C6F5H 41,42 ), and degree of shielding effect in 1 H NMR was reported to be different between a fluoroaromatic and a benzene ring, which might be the case in 119 Sn NMR.…”

“…14,22 On the other hand, we have recently reported on copper-catalyzed arylstannylation of arynes, which proceeds via the Sn/Cu transmetalation in an ethereal solvent, 1,2-diethoxyethane (DEE). [23][24][25] This result in conjunction with advantages of ethereal solvents (e.g., unique media in cross-coupling reactions; 26 environmentally friendly characteristics as represented by biomass-derived 2-MeTHF; 27 suitability for cross-coupling-based polymer syntheses 28 ) motivated us to explore fully the Pd/Cu-cocatalyzed MKSC in ethereal solvents without preconceived ideas.…”