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82 % EJZ mixture

Treatment of key intermediate 88 with methoxide led to a toluene-type compound 89. An intramolecular Wittig reaction can also be achieved to yield 2-substituted indole 90. The addition of an aldehyde resulted in a stilbene, e.g., 91 [87].

Procedure:Transformation of phosphonium salt 88 into Wittig product 91: The polymer-bound phosphonium bromide 88 (500 mg, 1.53 mmol/g) in dry MeOH (15 mL) was treated with 0.9 mL of a 2 M sodium methoxide solution followed by addition of methyl 4-formylbenzoate (1.8 mmol, 295 mg).This was heated under reflux for 2 h, cooled and then treated with glacial acetic acid (0.5 mL) and (carboxymethyl)trimethylammonium chloride hydrazide (2.7 mmol, 452 mg). After stirring overnight at rt (reaction with excess of aldehyde), the mixture was filtered over Kieselguhr and washed with DCM.The filtrate was washed with water (three times) and brine, dried over Na2S04 and evaporated to yield a 3:1 mixture of (E)- and (Z)-stilbenes (82 %).

3.1.3.5 Decarboxylation-Based Traceless Linking

This concept is based on the decarboxylation of P-keto carboxylic acids. Commercially available 2-aroyl acrylic acid 92 as starting material was coupled to trityl-modified resin. This step was followed by a Michael-type addition of indolines [88], Upon cleavage, the released intermediates 93 are decarboxylated to afford the desired p-indolinyl propiophenones 94 (Scheme 44).

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