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7b In our case the side-reaction with phosphines is described in Scheme
[2]
.
8
Coupling Reaction of Ylides 5 and 9 with Arylboronic Acids 6; General Procedure. A degassed solution of arylboronic acid (1.1 mmol) and P(t-Bu)3 (0.1 mmol) in DME-H2O (4:1, 10 mL) was added to a degassed flask containing a mixture of ylide 5 or 9 (0.5 mmol), LiOH·H2O (2.7 mmol), and Pd(OAc)2 (6 mg, 4 mmol%) and the resulting suspension was stirred at r.t. under Ar for 5 h. The solution was acidified to pH 6 by the addition of 4-5 drops of acetic acid and excess DME was evaporated. CH2Cl2 (10 mL) was added and the suspension was filtered through filter paper, which was moistened with CH2Cl2 (1-2 mL). The filtrate was dried, concentrated, and subjected to column chromatography (silica gel, hexanes-EtOAc, 3:1) to afford the coupling products 7 and 10. 2-Hydroxy-3-(3-thienyl)-1,4-naphthoquinone (
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10 The coupling reaction was repeated exactly under the previously described conditions, using 1 mmol of iodobenzene instead of ylide 5
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