Synthetic scope and DFT analysis of the chiral binap–gold(I) complex-catalyzed 1,3-dipolar cycloaddition of azlactones with alkenes

Martín-Rodríguez, María; Castelló, Luis M.; Nájera, Carmén; Sansano, José M.; Larrañaga, Olatz; Cózar, Abel de; Cossío, Fernando P.

doi:10.3762/bjoc.9.280

Cited by 8 publications

(11 citation statements)

References 42 publications

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“…The NICS value of -7.3 ppm pointed to the aromaticity of that ring in the ylide. These results explain the existence of different regioselectivities for both possible ylides (Scheme 20) [71,72].…”

Section: Scheme 19mentioning

confidence: 90%

“…Oxazolone derived from glycine 37a was allowed to react with N-phenylmaleimide (NPM) at room temperature using a 5 mol% of the chiral catalytic complex and a 5 mol% of base (Scheme 18) [71,72]. After completion, a large excess of trimethylsilyldiazomethane was added to obtain the methyl ester of intermediate carboxylic acid 39 (30 min), resulting from ring opening of the biciclic transient species 38.…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

“…N-Substituted methyl, and ethyl maleimides did not afford compounds 40 with so high enantioselections (60 and 70% ee, respectively), however N-phenyl or Narylmaleimides gave very good enantioselections of compounds 40a-40c in high chemical yields (Scheme 19). The variation of the arene substituent of the azlactones (even working with an heteroaromatic substituent, such as 2-thienyl) promoted also excellent to good enantioselections in compounds 40d-40f (Scheme 19) [71,72].…”

Section: Scheme 18mentioning

confidence: 99%

“…The less energetic computed TS are depicted on Figure 9 where the gold atom is coordinated only to the azlactone by the nitrogen atom. This reaction completely failed when chiral silver(I) complexes were attempted [72]. The less reactive alanine-derived 4-methyloxazole-5-one 41 under these reaction conditions only reacted at 25 and at 0 ºC with tert-butyl acrylate yielding cycloadduct 42 in good yields and moderate to good enantioselections (Scheme 20).…”

Section: Scheme 19mentioning

confidence: 99%

“…If we compare these results with previous ones obtained using α-imino esters, this last diastereoselective cycloaddition exhibited an opposite regioselection. Besides, the resulting relative configuration of ∆ 1 -pyrroline 42 is equivalent to the exo-approach of the dipolarophile when an endo-transition state was the most favourable in the gold(I)-catalyzed 1,3-DC with α-imino esters and alkenes [72].…”

Section: Scheme 19mentioning

confidence: 99%

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Coinage metal complexes as chiral catalysts for 1,3-dipolar cycloadditions

Nájera

Sansano

2014

Journal of Organometallic Chemistry

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In this account, we describe the experience of our research group in the implementation of chiral coinage metal complexes into the efficient enantioselective 1,3-DC of azomethine ylides derived from α-amino acids and azlactones with different dipolarophiles. The corresponding chiral metallodipoles were generated in situ and next focused on the synthesis of highly substituted prolines. For this purpose, privileged ligands such as phosphoramidites and binap with silver(I), gold(I) and copper(II) salts are described. Depending from the ligand and mainly from the metal salt it can be possible to control the facial endo/exo-diasteroselectivity and the enantioselectivity of these types of processes. The synthetic processes are also supported by DFT calculations in order to elucidate the most plausible mechanism and the stereochemical results.

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Section: Scheme 19mentioning

confidence: 90%

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

Section: Scheme 18mentioning

confidence: 99%

Section: Scheme 19mentioning

confidence: 99%

Section: Scheme 19mentioning

confidence: 99%

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Coinage metal complexes as chiral catalysts for 1,3-dipolar cycloadditions

Nájera

Sansano

2014

Journal of Organometallic Chemistry

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Asymmetric Synthesis of Quaternary α‐Amino Acids and Their Phosphonate Analogues

2014

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Asymmetric synthesis of α‐amino acids and their phosphonate analogues has received considerable attention due to their diverse biological activities. Quaternary α‐amino acids and their phosphonate analogues are often more resistant to chemical and enzymatic degradation and therefore have been targets of various synthetic endeavors. This Focus Review provides a summary of recent approaches to catalytic asymmetric synthesis of quaternary α‐amino acids and α‐aminophosphonates.

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Gold‐Catalyzed Enantioselective Annulations

Zhang

2016

Chemistry A European J

214

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Non-oxidative,regioselective,and convergent access to densely functionalized oxazoles is realized in af unctional-group tolerant manner using alkynyl thioethers.S ulfur-terminated alkynes provideaccess to reactivity previously requiring strong donor-substituted alkynes such as ynamides.Sulfur does not act in an analogous donor fashion in this gold-catalyzed reaction, thus leading to complementary regioselective outcomes and addressing the limitations of using ynamides. Compared to other heteroatom-substituted alkynes,alkynyl thioethers are remarkably little explored in intermolecular late-transition-metal catalysis,d espite being readily accessed and robust. [1, 2] Ynamides,i nc ontrast, are privileged sub-strates:i np-acid catalysis their donor nature aids metal-alkyne coordination and affords highly polarized electro-philes,t hus providing the high chemo-and regioselectivity required for the discovery of efficient intermolecular reactions (Scheme 1a). [3,4] As the resulting inclusion of ad onor-nitrogen atom limits the utility of the products,r etaining the reactivity profile of these transformations whilst accessing more flexible and readily elaborated substitution patterns would be desirable.T he value of sulfur-substituted compounds [5] coupled with progress in C À Ca nd C-heteroatom bond formation from CÀSbonds, [6] renders alkynyl thioethers appealing alternatives to ynamides.I ndeed the ketenethio-nium pathway (Scheme 1a)f rom alkynyl thioethers has recently been invoked in proton-catalyzed reactions with nitriles [2g,h] and gold-catalyzed reactions with sulfides. [2i] Ynamides enabled the discovery of formal [3+ +2] dipolar cycloadditions with nucleophilic nitrenoids, [7] thus allowing intermolecular access to a-imino gold carbene-type reactivity for heterocycle synthesis (Scheme 1b). [8, 9] Such reactions, which do not depend on ynamides,a re scarce. [8b,h] As trong donor alkyne substituent proved critical in the formation of oxazoles using N-acyl pyridinium N-aminides,aselectron-rich alkynes such as anisole derivatives did not react (Scheme 1b, inset). [8a,b] Oxazoles are valuable synthetic intermediates [10,11] and structural components in bioactive natural products, [12] agrochemicals, [13] ligands, [14] and functional materials. [15] Despite recent advances,asingle modular and convergent route to trisubstituted oxazoles,which provides the structural and functional-group diversity needed across the 2-, 4-, and 5-positions,r emains unrealized. [16] Following our interest in the use of gold catalysis with sulfides [17] we report here on the reactivity of alkynyl thioethers with nucleophilic nitrenoids to prepare oxazoles. Importantly,t he regioselectivity is not consistent with ac on-trolling ketenethionium species.T he sulfur group plays an alternative role in enabling reactivity,t hus proving complementary to donor-enabled approaches. Ther eaction of the alkynyl thioether 1a and aminide 2a (Table 1) showed that conversion into the oxazole 3 was possible at 125 8 8Ci n1 ,2-dichlorobenzene (1,2-DCB;s ...

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Synthetic scope and DFT analysis of the chiral binap–gold(I) complex-catalyzed 1,3-dipolar cycloaddition of azlactones with alkenes

Cited by 8 publications

References 42 publications

Coinage metal complexes as chiral catalysts for 1,3-dipolar cycloadditions

Coinage metal complexes as chiral catalysts for 1,3-dipolar cycloadditions

Asymmetric Synthesis of Quaternary α‐Amino Acids and Their Phosphonate Analogues

Gold‐Catalyzed Enantioselective Annulations

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