Borane reduction of 3-substituted-2-indolinones

McEvoy, Francis J.; Allen, George R.

doi:10.1021/jo00959a024

Cited by 16 publications

(11 citation statements)

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“…The aqueous solution was thoroughly extracted with EtOAc and the extract washed with brine, dried, and evaporated. Purification by VLC, eluting with hexane−EtOAc (40:60 → 0:100), gave tryptophol (7 mg, 3%) and the alcohol ( 6 ) (250 mg, 83%): mp 112−14 °C (lit . mp 111−112 °C); anal .…”

Section: Methodsmentioning

confidence: 99%

Total Synthesis of Donaxaridine

1997

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Section: Methodsmentioning

confidence: 99%

Total Synthesis of Donaxaridine

1997

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“…13c,30 On the other hand, refluxing mixtures of BH 3 •THF and 2-oxindolylacetic acid derivatives in THF yielded the respective indoline ethanols in 43-79%. 31 The ketone carbonyl of isatin derivatives is susceptible to nucleophilic attack and aldol type condensations are readily performed under a variety of conditions. 21 It was therefore reasoned that these aldol products should readily undergo reduction with borane in THF to yield tryptophols.…”

Section: Introductionmentioning

confidence: 99%

A versatile synthetic methodology for the synthesis of tryptophols

2002

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Tryptophols have been obtained in high yields by the reduction of 3-substituted-dioxindoles (obtained by the aldol condensation reaction of ketones with isatins or by a modified Knovenagel malonate condensation) using a borane tetrahydrofuran complex. The reported methodology offers distinct advantages over existing methods for the synthesis of these compounds, including consistently greater yields, diastereoselective syntheses and the possibility for the synthesis of a wide range of structurally different tryptophols. The reduction reaction was found to proceed via an intermediate 1,3-diol-oxindole, which was obtained diastereoselectively and, which was subsequently reduced to the corresponding tryptophol.

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“…4 As part of an endeavor to broaden the scope of the method, the possible replacement of the indole ring by the oxindole nucleus among early synthetic intermediates came under scrutiny. This modification offered great promise, since the resulting oxindoloindolizidine (7) could be envisaged in various stereochemical and substituted forms to be on the route to oxindole alkaloids of the rhyncophylline and mitraphylline types, to Aspidosperma alkaloids,5 and to structures of even greater complexity. The incorporation of the oxindole system in the present scheme of synthesis appeared feasible at three stages of the reaction sequence: (a) by starting the sequence with oxytryptophol (5), (b) by oxidative conversion of indole 3 into oxindole 6 (followed by cyclization), and (c) by a related transformation of 4 into 7.…”

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confidence: 99%

“…Bromination of tryptophol (1) in acetic acid gave a bromooxindole whose hydrogenolysis6 led to oxytryptophol (5). 7 Unfortunately, in analogy with previous experience on lY-methyloxindole compounds,8 attempts of conversion of oxytryptophol (5) into an alkylating agent by the replacement of its hydroxy function by a leaving group failed. Thus, for example, treatment of 5 with hydrobromic acid yielded cyclopropane 8.9|1°As a consequence the preparation of oxindole equivalents of salts 2 appears a difficult task at best and the introduction of the oxindole unit is preferable at a later stage of Scheme I.…”

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confidence: 99%