Stereoselective Synthesis of Z-Alkenes

Siau, Woon‐Yew; Zhang, Yao; Zhao, Yu

doi:10.1007/128_2012_315

Cited by 131 publications

(72 citation statements)

References 78 publications

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“…In this work we report that upon heating of aminoborane 6 at 80 °C under 2 bar H 2 new signals different from those of 6 or 7 in the 1 H, 19 F and 10 B NMR spectra appear along with formation of C 6 F 5 H. The new species was isolated as a greenish oil and identified as the hydroborane 8 ( Fig. 2a) Since 8 is a potentially hydroborating BH-species and can be produced in situ from 6, we attempted to use 8 as a catalyst in hydrogenation of unactivated alkenes and alkynes following the strategy depicted in Various dialkyl-, diaryl-, arylalkylacetylenes were successfully hydrogenated under standard conditions:…”

Section: New Ansa-aminohydroborane As a Catalystmentioning

confidence: 66%

“…19 F NMR spectrum revealed complete cleavage of the C 6 F 5 -group into C 6 F 5 H. Evidently, the inability to hydrogenate terminal alkynes is a result of the catalysts degradation into species inert to hydrogen due to complete elimination of the perfluorophenyl groups. …”

Section: Alkenes Under Hydrogenation Conditionsmentioning

confidence: 96%

“…Stereoselective hydrogenation of alkynes is an important protocol in synthesis of natural and industrially relevant compounds. 19,20,21,22,23 . Heterogeneous as well as homogeneous metal catalysts for this purpose are known 24,25,26,27,28 , however, metal-free catalytic hydrogenation of unactivated alkynes into alkenes has not been reported previously.…”

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confidence: 99%

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A frustrated-Lewis-pair approach to catalytic reduction of alkynes to cis-alkenes

et al. 2013

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Recently, a new approach to dihydrogen activation known as frustrated Lewis pairs (FLPs) concept has been introduced 1, 2, 3 . A combination of highly Lewis acidic boranes and sterically hindered bases can split hydrogen heterolytically generating onium (phosphonium, ammonium, etc.) borohydrides. These compounds show reduction activity resembling that of inorganic borohydrides like NaBH 4 , i. e. they are suitable mostly for reduction of polarized multiple bonds. Imines, enamines, silyl ethers 4, 5,6 , α,β-enones 7 , ynones 8 , Nalkylanilines 9 were hydrogenated using stoichiometric or catalytic amounts of FLPs. Due to heterolytic nature of FLP-H 2 adducts, hydrogenation of unactivated multiple C-C bonds using FLPs has some natural limitations, since during the respective step of the catalytic cycle a proton transfer from catalyst to substrate should take place (Fig. 1a). Although Greb et al. have implemented this approach to hydrogenation of alkenes under ambient conditions, this method is predictably restricted to the alkenes with high proton affinity 10 .

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Section: New Ansa-aminohydroborane As a Catalystmentioning

confidence: 66%

Section: Alkenes Under Hydrogenation Conditionsmentioning

confidence: 96%

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A frustrated-Lewis-pair approach to catalytic reduction of alkynes to cis-alkenes

et al. 2013

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“…Linear E - and Z -trisubstituted alkenes occur widely in nature and are used regularly in preparative chemistry 1,2 (for example, in catalytic enantioselective hydrogenations 3 , allylic substitutions 4 , or conjugate additions 5 ). Several approaches have been developed for generating acyclic trisubstituted alkenes, but these have key shortcomings.…”

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confidence: 99%

Synthesis of E- and Z-trisubstituted alkenes by catalytic cross-metathesis

Nguyen

Koh

Mann

et al. 2017

Nature

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Catalytic cross-metathesis is a central transformation in chemistry, and yet, corresponding methods for stereoselectively generating acyclic trisubstituted alkenes in either isomeric form do not exist. The key problems are lack of chemoselectivity, namely, the preponderance of side reactions involving only the less hindered starting alkene, ensuing nonproductive processes of homo-metathesis byproducts, and formation of short-lived methylidene complexes. In contrast, in catalytic cross-coupling, another widely used process, substrates are more distinct and homocoupling is less of a problem. Here, we show that through cross-metathesis reactions involving E- or a Z-trisubstituted alkenes, easily prepared from commercially available starting materials by cross-coupling processes, many otherwise desirable and difficult-to-access linear E- or Z-trisubstituted alkenes can be synthesized efficiently and in exceptional stereoisomeric purity (up to >98% E or 95% Z). Utility is highlighted through concise stereoselective syntheses of biologically active compounds such as indiacen B (anti-fungal) and coibacin D (anti-inflammatory).

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“…In contrast, using DMF as the solvent resulted in a smooth conversion of alkynes 3a-3d to afford the corresponding cis-alkenes 4a-4d in typically 2-5 days and in good yields (81%-93%). Although the partial hydrogenation of alkynes with Lindlar catalyst has been used frequently, solvent effects as well as effects of sterical crowdedness seem to be hardly assessable, and the conditions often need rigorous optimization regarding the individual reaction system [16][17][18][19]. Therefore, we believe the protocol described above might be of further use for the partial hydrogenation of comparable branched alkyne systems.…”

Section: Resultsmentioning

confidence: 99%

2-C-Alkynyl and 2-C-cis-Alkenyl β-Mannosides with Acetal Protected γ-Aldehyde Functionality via 2-Uloside Alkynylation and Lindlar Hydrogenation

Borowski

Menzel

Ziegler

2016

Molbank

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Abstract:Benzyl 3,4,6-tri-O-benzyl-β-D-arabino-hexos-2-ulo-1,5-pyranoside was subjected to mannoselective ketone alkynylation with propiolaldehyde dibenzyl acetal, resulting in the formation of a 2-C-alkynyl β-mannoside bearing a γ-dibenzyl acetal functionality. Subsequent transacetalization of the acetal moiety with methanol and 1,3-dihydroxypropane and acetylation of position 2, respectively, gave 4 different 2-C-alkynyl branched mannosides. Lindlar hydrogenation of the latter under optimized conditions in dimethylformamide afforded a series of 2-C-cis-alkenyl mannosides. X-ray molecular structures of benzyl 3,4,6-tri-O-benzyl-β-D-arabino-hexos-2-ulo-1,5-pyranoside and of the branched glycoside benzyl 3,4,6-tri-O-benzyl-2-C-((Z)-3,3-dibenzyloxyprop-1-en-1-yl)-β-Dmannopyranoside are reported.

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Stereoselective Synthesis of Z-Alkenes

Abstract: This chapter offers a general review of the evolvement of methods for the stereoselective synthesis of Z-alkenes, with a focus on the development of catalytic systems towards this goal in recent years.

Cited by 131 publications

References 78 publications

A frustrated-Lewis-pair approach to catalytic reduction of alkynes to cis-alkenes

A frustrated-Lewis-pair approach to catalytic reduction of alkynes to cis-alkenes

Synthesis of E- and Z-trisubstituted alkenes by catalytic cross-metathesis

2-C-Alkynyl and 2-C-cis-Alkenyl β-Mannosides with Acetal Protected γ-Aldehyde Functionality via 2-Uloside Alkynylation and Lindlar Hydrogenation

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