Novel method for the synthesis of isomerically pure vinyl halides from alkynes via the hydroalumination reaction

Zweifel, George; Whitney, Charles C.

doi:10.1021/ja00987a054

Cited by 174 publications

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“…Functionalization of the internal acetylene of 7a was realized through standard Pd-catalyzed hydrostannylation conditions to initially provide vinyl stannane 57 in only 25% yield along with recovered starting material (Scheme 17). Screening of other hydrometallation protocols, including hydrozirconation, 45 hydroboration, 46 and hydroalumination, 47 either resulted in recovery of starting material or reduction of the N -Ts lactam moiety. The steric congestion around this internal alkyne due to the cyclohexyl ring and adjacent quaternary carbon posed a considerable challenge to this otherwise standard transformation.…”

Section: Resultsmentioning

confidence: 99%

Total Synthesis of the Spirocyclic Imine Marine Toxin (−)-Gymnodimine and an Unnatural C4-Epimer

Kong¹,

Moussa²,

Lee³

et al. 2011

J. Am. Chem. Soc.

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The first total synthesis of the marine toxin (−)-gymnodimine (1) has been accomplished in a convergent manner. A highly diastereo- and enantioselective exo-Diels–Alder reaction catalyzed by a bis-oxazoline Cu(II) catalyst enabled rapid assembly of the spirocyclic core of gymnodimine. The preparation of the tetrahydrofuran fragment utilized a chiral auxiliary based anti-aldol reaction. Two major fragments, spirolactam 56 and tetrahydrofuran 55, were then coupled through an efficient Nozaki–Hiyama–Kishi reaction. An unconventional, ambient temperature t-BuLi-initiated intramolecular Barbier reaction of alkyl iodide 64 was employed to form the macrocycle. A late stage vinylogous Mukaiyama aldol addition of a silyloxyfuran to a complex cyclohexanone 83 appended the butenolide and a few additional steps provided (−)-gymnodimine (1). A diastereomer of the natural product was also synthesized, C4-epi-gymnodimine (90), derived from the vinylogous Mukaiyama aldol addition.

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Section: Resultsmentioning

confidence: 99%

Total Synthesis of the Spirocyclic Imine Marine Toxin (−)-Gymnodimine and an Unnatural C4-Epimer

Kong¹,

Moussa²,

Lee³

et al. 2011

J. Am. Chem. Soc.

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“…The (Z,E) isomer was prepared by the sequence shown in Scheme 1 (1). (E)-12-Pentadecen-10-yn-1-ol THP was prepared by palladium-catalyzed cross-coupling of 10-undecyn-1-ol THP (prepared from 10-undecyn-1-ol and dihydropyran) with E-1-iodo-1-butene (Zweifel and Whitney 1967;Alami et al 1993). Addition of dicyclohexyl borane across the triple bond followed by hydrolysis of both the borane and THP protecting group gave the desired (Z,E) diene stereochemistry (Brown 1975).…”

Section: Insect Rearing Pheromone Extraction and Fractionationmentioning

confidence: 99%

Unusual pheromone chemistry in the navel orangeworm: novel sex attractants and a behavioral antagonist

Leal

Parra-Pedrazzoli

Kaissling

et al. 2005

Naturwissenschaften

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Using molecular- and sensory physiology-based approaches, three novel natural products, a simple ester, and a behavioral antagonist have been identified from the pheromone gland of the navel orangeworm, Amyelois transitella Walker (Lepidoptera: Pyralidae). In addition to the previously identified (Z,Z)-11,13-hexadecadienal, the pheromone blend is composed of (Z,Z,Z,Z,Z)-3,6,9,12,15-tricosapentaene, (Z,Z,Z,Z,Z)-3,6,9,12,15-pentacosapentaene, ethyl palmitate, ethyl-(Z,Z)-11,13-hexadecadienoate, and (Z,Z)-11,13-hexadecadien-1-yl acetate. The C(23) and C(25) pentaenes are not only novel sex pheromones, but also new natural products. In field tests, catches of A. transitella males in traps baited with the full mixture of pheromones were as high as those in traps with virgin females, whereas control and traps baited only with the previously known constituent did not capture any moths at all. The navel orangeworm sex pheromone is also an attractant for the meal moth, Pyralis farinalis L. (Pyralidae), but (Z,Z)-11,13-hexadecadien-1-yl acetate is a behavioral antagonist. The new pheromone blend may be highly effective in mating disruption and monitoring programs.

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“…Bromoalkenes are the preferred starting material for the generation of the corresponding nucleophile 13, since many are commercially available or readily prepared [52,53,54,55,56]. Whilst the methodology is also efficient when iodo-alkenes are used as the precursors for the organoaluminium reagent, a very precise temperature protocol must be followed and Et2AlCl provides better results in the transmetalation process [44,45].…”

Section: Organoaluminium Reagents As Nucleophilesmentioning

confidence: 99%

Formation of Quaternary Stereocentres by Copper-Catalysed Enantioselective Conjugate Addition Reaction

Maciá

2015

Progress in Enantioselective Cu(I)-Catalyzed Formation of Stereogenic Centers

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Remarkable progress in copper catalysed enantioselective conjugate addition (ECA) reactions has been made over the past decade. This enantioselective transformation now allows the challenging formation of chiral quaternary centres by addition of different nucleophiles to trisubstituted ,unsaturated systems. This chapter summarizes the developments in the area.to overcome this barrier and allow the synthesis of quaternary stereogenic centres with very good selectivities [32,33], as it will be presented in the following pages of this chapter. Alternative strategies to facilitate the copper catalysed formation of quaternary chiral centres include the activation of the ,-disubstituted ,-unsaturated systems (by making the β-position more electrophilic) by using Lewis-acidic nucleophiles or by the implementation of additional electronwithdrawing functionalities in the substrate.This chapter is an overview of the copper-based catalytic systems that enable the formation of chiral quaternary centres through conjugate addition reactions. The existing methodologies have been classified in three main sections, according to the nature of the nucleophile that participates in the ECA reaction. Thus, Section 2 covers carbon nucleophiles, including organoaluminium (section 2.1), Grignard (section 2.2), organozinc (section 2.3) and organozirconium reagents (section 2.4). Next, Section 3 reviews the use of organoboron reagents, to form boron containing quaternary centres. And last, Section 4 presents the use of organosilicon reagents, to form silicon containing quaternary centres.After the ECA reaction step, the generated enolate requires protonation to generate the corresponding enol, which rapidly tautomerises to the ketone product. Protonation is typically carried out by addition of water, aqueous NH4Cl or aqueous HCl. For simplicity, this step has been omitted in all schemes, and only the conditions for the ECA have been presented. * Strangely, the use of two equivalents of MeLi gave poor processes -despite the known efficacy of Me2AlCH≡CHR species in related processes. Scheme 14. Copper catalysed ECA of organoaluminium reagents to -aryl cyclohexenones by Alexakis [47,48].Regarding the challenging -substituted cyclopenten-2-one substrates, phosphinamine ligands give moderate, comparable enantioselectivities to phosphoramidites, as shown in Scheme 15.Scheme 15. Copper-phosphinamine catalysed ECA of organoaluminium reagents to -substituted cyclopentenones by Alexakis [47,48].The tandem hydroalumination-ECA process to β-substituted cyclic enones with phosphinamine ligands also works very efficiently (Scheme 16) [49,50]. The best copper source for this catalytic system is copper (II) naphthenate, which is cheaper than the CuTC used in previous methodologies and can be used as a stock solution. A wide range of alkenylaluminium reagents can be added with

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Novel method for the synthesis of isomerically pure vinyl halides from alkynes via the hydroalumination reaction

Cited by 174 publications

References 0 publications

Total Synthesis of the Spirocyclic Imine Marine Toxin (−)-Gymnodimine and an Unnatural C4-Epimer

Total Synthesis of the Spirocyclic Imine Marine Toxin (−)-Gymnodimine and an Unnatural C4-Epimer

Unusual pheromone chemistry in the navel orangeworm: novel sex attractants and a behavioral antagonist

Formation of Quaternary Stereocentres by Copper-Catalysed Enantioselective Conjugate Addition Reaction

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