α,α‐Diarylprolinol Ethers: New Tools for Functionalization of Carbonyl Compounds

Mielgo, Antonia; Palomo, Claudio

doi:10.1002/asia.200700417

Cited by 409 publications

(93 citation statements)

References 326 publications

(204 reference statements)

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“…The direct chiral amine 5 a [16] and [PdA C H T U N G T R E N N U N G (PPh 3 ) 4 ] co-catalyzed enantioselective a-allylation of aldehyde 1 a with 2 a gave the corresponding alcohol 4 a (after in situ reduction of 3 a) as a single regioisomer with 75:25 e.r. (e.r.…”

Section: Resultsmentioning

confidence: 99%

Direct Regiospecific and Highly Enantioselective Intermolecular α‐Allylic Alkylation of Aldehydes by a Combination of Transition‐Metal and Chiral Amine Catalysts

Afewerki¹,

Ibrahem²,

Rydfjord³

et al. 2012

Chemistry A European J

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The first direct intermolecular regiospecific and highly enantioselective α-allylic alkylation of linear aldehydes by a combination of achiral bench-stable Pd(0) complexes and simple chiral amines as co-catalysts is disclosed. The co-catalytic asymmetric chemoselective and regiospecific α-allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2-alkyl alcohols with high enantiomeric ratios (up to 98:2 e.r.; e.r.=enantiomeric ratio). It is also an expeditious entry to valuable 2-alkyl substituted hemiacetals, 2-alkyl-butane-1,4-diols, and amines. The concise co-catalytic asymmetric total syntheses of biologically active natural products (e.g., Arundic acid) are disclosed.

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Section: Resultsmentioning

confidence: 99%

Direct Regiospecific and Highly Enantioselective Intermolecular α‐Allylic Alkylation of Aldehydes by a Combination of Transition‐Metal and Chiral Amine Catalysts

Afewerki¹,

Ibrahem²,

Rydfjord³

et al. 2012

Chemistry A European J

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“…It was encouraging to find that chiral pyrrolidines 8 and 9 produced more products in 4 h but with no diastereoselectivity (Table 1, entries 4-5). To our delight, the TMS-protected dipenylprolinol 10 [29] catalyzed the enantioselective formation of 2-formyl-aziridine 3 a in 86 % conversion after 3 h with 9:1 d.r. and 99 % ee (entry 6).…”

Section: Resultsmentioning

confidence: 99%

Catalytic Asymmetric Aziridination of α,β‐Unsaturated Aldehydes

Deiana

Dziedzic

Zhao

et al. 2011

Chemistry A European J

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The development, scope, and application of the highly enantioselective organocatalytic aziridination of α,β-unsaturated aldehydes is presented. The aminocatalytic azirdination of α,β-unsaturated aldehydes enables the asymmetric formation of β-formyl aziridines with up to >19:1 d.r. and 99% ee. The aminocatalytic aziridination of α-monosubstituted enals gives access to terminal α-substituted-α-formyl aziridines in high yields and up to 99% ee. In the case of the organocatalytic aziridination of disubstituted α,β-unsaturated aldehydes, the transformations were highly diastereo- and enantioselective and give nearly enantiomerically pure β-formyl-functionalized aziridine products (99% ee). A highly enantioselective one-pot cascade sequence based on the combination of asymmetric amine and N-heterocyclic carbene catalysis (AHCC) is also disclosed. This one-pot three-component co-catalytic transformation between α,β-unsaturated aldehydes, hydroxylamine derivatives, and alcohols gives the corresponding N-tert-butoxycarbonyl and N-carbobenzyloxy-protected β-amino acid esters with ee values ranging from 92-99%. The mechanisms and stereochemistry of all these catalytic transformations are also discussed.

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“…In 2005, Jørgensen and co-workers [13], and Hayashi et al [14], independently, discovered that diphenylprolinol silyl ether is an effective organocatalyst [15] [16]. Hayashi et al reported its application for the highly enantioselective, catalytic Michael addition of aldehydes to nitro alkenes.…”

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confidence: 97%

Organocatalyzed Michael Addition of Aldehydes to Nitro Alkenes – Generally Accepted Mechanism Revisited and Revised

Patora-Komisarska

Benohoud

Ishikawa

et al. 2011

Helvetica Chimica Acta

197

127

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The amine-catalyzed enantioselective Michael addition of aldehydes to nitro alkenes (Scheme 1) is known to be acid-catalyzed (Fig. 1). A mechanistic investigation of this reaction, catalyzed by diphenylprolinol trimethylsilyl ether is described. Of the 13 acids tested, 4-NO 2 ÀC 6 H 4 OH turned out to be the most effective additive, with which the amount of catalyst could be reduced to 1 mol-% (Tables 2 -5). Fast formation of an amino-nitro-cyclobutane 12 was discovered by in situ NMR analysis of a reaction mixture. Enamines, preformed from the prolinol ether and aldehydes (benzene/molecular sieves), and nitroolefins underwent a stoichiometric reaction to give single all-trans-isomers of cyclobutanes (Fig. 3) in a [2 þ 2] cycloaddition. This reaction was shown, in one case, to be acid-catalyzed (Fig. 4) and, in another case, to be thermally reversible (Fig. 5). Treatment of benzene solutions of the isolated aminonitro-cyclobutanes with H 2 O led to mixtures of 4-nitro aldehydes (the products 7 of overall Michael addition) and enamines 13 derived thereof (Figs. 6 -9). From the results obtained with specific examples, the following tentative, general conclusions are drawn for the mechanism of the reaction (Schemes 2 and 3): enamine and cyclobutane formation are fast, as compared to product formation; the zwitterionic primary product 5 of C,C-bond formation is in equilibrium with the product of its collapse (the cyclobutane) and with its precursors (enamine and nitro alkene); when protonated at its nitronate anion moiety the zwitterion gives rise to an iminium ion 6, which is hydrolyzed to the desired nitro aldehyde 7 or deprotonated to an enamine 13. While the enantioselectivity of the reaction is generally very high (> 97% ee), the diastereoselectivity depends upon the conditions, under which the reaction is carried out (Fig. 10 and Tables 1 -5). Various acid-catalyzed steps have been identified. The cyclobutanes 12 may be considered an off-cycle reservoir of catalyst, and the zwitterions 5 the key players of the process (bottom part of Scheme 2 and Scheme 3).

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α,α‐Diarylprolinol Ethers: New Tools for Functionalization of Carbonyl Compounds

Cited by 409 publications

References 326 publications

Direct Regiospecific and Highly Enantioselective Intermolecular α‐Allylic Alkylation of Aldehydes by a Combination of Transition‐Metal and Chiral Amine Catalysts

Direct Regiospecific and Highly Enantioselective Intermolecular α‐Allylic Alkylation of Aldehydes by a Combination of Transition‐Metal and Chiral Amine Catalysts

Catalytic Asymmetric Aziridination of α,β‐Unsaturated Aldehydes

Organocatalyzed Michael Addition of Aldehydes to Nitro Alkenes – Generally Accepted Mechanism Revisited and Revised

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