2013
DOI: 10.1002/adsc.201300359
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Relay Redox and Lewis Acid Catalysis in the Titanocene‐ Catalyzed Multicomponent Assembly of 1,5‐Enynes

Abstract: Herein we describe a direct, multicomponent assembly of 1,5-enynes. The titanocene-catalyzed coupling of an aryl aldehyde, iodoalkyne, and allylsilane enables the convergent and rapid synthesis of this versatile architectural motif in good to excellent yields.

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Cited by 16 publications
(8 citation statements)
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“…Ashfeld advanced Ti-promoted redox–Lewis acid relay catalysis for the three-component coupling of aldehydes ( 54 ), iodoacetylides ( 55 ), and nucleophiles ( 56 ; Scheme ). In this reaction, the Ti catalyst is proposed to take on multiple roles in the mechanism by behaving as both a Lewis acid and a single-electron reductant. The reaction begins with the reductive activation of 55 by Cp 2 Ti III Cl to form Ti IV -acetylide 58 .…”
Section: Net-reducing Methodologymentioning
confidence: 99%
See 1 more Smart Citation
“…Ashfeld advanced Ti-promoted redox–Lewis acid relay catalysis for the three-component coupling of aldehydes ( 54 ), iodoacetylides ( 55 ), and nucleophiles ( 56 ; Scheme ). In this reaction, the Ti catalyst is proposed to take on multiple roles in the mechanism by behaving as both a Lewis acid and a single-electron reductant. The reaction begins with the reductive activation of 55 by Cp 2 Ti III Cl to form Ti IV -acetylide 58 .…”
Section: Net-reducing Methodologymentioning
confidence: 99%
“…For example, chromones and quinolones with pendent nitrile groups (41) can undergo reductive ketone− nitrile cyclization to yield product 42 (Scheme 5B). 42−44 developed an enantioselective variant of the reductive ketone− nitrile cyclization using Brintzinger's ansa-titanocene complex (48), providing efficient access to enantioenriched αhydroxyketones (49) with a fully substituted stereocenter (Scheme 6). 45,46 2.3.…”
Section: Introductionmentioning
confidence: 99%
“…The combined organic layers were washed with brine, dried under anhydrous Na 2 SO 4 , and concentrated under reduced pressure to yield the crude product, which was purified by column chromatography on silica gel (eluent: hexane/EtOAc = 20:1) to afford a yellow solid (71 mg, 81% yield): 1 H NMR (CDCl 3 , 400 MHz, δ) 7.36 (d, J = 8.9 Hz, 2H), 6.59 (d, J = 8.9 Hz, 2H), 2.99 (s, 6H, N(CH 3 ) 2 ); 13 C{ 1 H} NMR (CDCl 3 , 100.6 MHz, δ) 150.9 (q), 134.5 (t), 111.7 (t), 106.8 (q), 79.2 (q), 75.8 (q), 73.6 (q), 40.2 (p), 0.4 (q); IR (cm (Iodobuta-1,3-diyn-1-yl)benzene (7d). 146 This compound was synthesized in accordance with method B from buta-1,3-diyn-1ylbenzene (5d) (300.0 mg, 2.38 mmol). The crude product was purified by column chromatography (eluent: hexane/acetone = 100:1) to afford a light brown solid (443 mg, 74% yield): 1 H NMR (CDCl 3 , 400.13 MHz, δ) 7.55−7.45 (m, 2H, Ar), 7.34 (m, 3H, Ar).…”
Section: Scheme 7 Electrophile-induced Cyclization Of Bis(ethynyl)tri...mentioning
confidence: 99%
“…Nevertheless, the main challenge with the proposed strategy resided in the enantioselective synthesis of enyne 1 . Most synthetic methods known to access 1,5-enynes take advantage of the reactivity of a propargylic cation generated through either catalytic or stoichiometric Lewis acid activation, allowing access only to racemic material . Morken et al showed recently that a Pd-catalyzed enantiospecific cross-coupling reaction gave 1,5-enynes with high enantiomeric excess starting from enantioenriched activated propargylic alcohols and allyl boronic esters .…”
mentioning
confidence: 99%