Camphor-10-sulfonamide-based prolinamide organocatalyst for the direct intermolecular aldol reaction between ketones and aromatic aldehydes

Rani, Rashmi; Peddinti, Rama Krishna

doi:10.1016/j.tetasy.2010.04.018

Cited by 28 publications

(16 citation statements)

References 65 publications

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“…Several aromatic aldehydes were used under these conditions, and the best results were achieved with those possessing electron-withdrawing groups [174]. Camphor-10-sulfonamide-based prolinamide 127 was an efficient catalyst for the reaction of aromatic aldehydes with cyclic ketones and acetone providing the aldols 54 in excellent enantioselectivities (88-99% ee) probably because of the shielding of one of the faces of the enamine by the benzyl moieties of the catalyst [175]. Sugar-based prolinamides Results achieved in the reaction between acetone and p-bromobenzaldehyde.…”

Section: Aldehydes As Electrophilesmentioning

confidence: 99%

Organocatalyzed Aldol Reactions

Guillena¹

2013

Modern Methods in Stereoselective Aldol Reactions

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The use of catalytic enantioselective methods to perform an aldol reaction provides a direct entry for the synthesis of chiral compounds and is probably the most attractive way to achieve this goal with high control of the chemo-, regio-, diastereo-, and enantioselectivity. The application of biochemical methods based on enzyme aldolases or antibodies, which are discussed in other chapters, avoid the use of preformed enolates or their equivalents for enhancing the global atom efficiency of the process [1] for which the narrow substrate scope is a major drawback. The discovery of methodologies to carry out the enantioselective direct aldol reaction [2] has eluded the production of stoichiometric by-products increasing the substrate scope. This task could be accomplished by using small molecules as catalysts, such as metal complexes (which are covered along this book) and organic molecules, also known as organocatalysts [3]. The growth of this last research area and the direct aldol reaction are closely linked [4], with the report on the use of (S)-proline as catalyst for the intermolecular aldol [5] definitely being the push for the development of the organocatalytic methods as a competitive methodology for the synthesis of chiral compounds.In a strict sense, an organocatalyzed reaction is a process in which all the involved reagents and catalysis are purely organic compounds of low-molecular weight, excluding boron-and silicon-containing derivatives. However, in some cases, the presence of a silyl group only plays a steric role and therefore can also be considered as an organocatalyzed process. Also, if the organocatalyst involved in a reaction is immobilized in a polymer, a dendrimer, or even an inorganic material that serves only as a support to facilitate its recovery [6], it could still be considered as an organocatalyst, although those types of derivatives have been scarcely used in the natural product synthesis and therefore will be excluded from this chapter. Therefore, a comprehensive overview of the direct aldol reaction [7], emphasizing the reactivity, scope, selectivity, and limitations of the methodology and giving several examples of their application to the synthesis of biologically active compounds, is discussed in this chapter.

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Section: Aldehydes As Electrophilesmentioning

confidence: 99%

Organocatalyzed Aldol Reactions

Guillena¹

2013

Modern Methods in Stereoselective Aldol Reactions

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“…Those are mainly five‐ and six‐membered cyclic sulfonyl hydrazine derivatives prepared from camphor sulfonic acid 11–14. However, there are also more noncovalent camphor‐derived organocatalysts, the bulk of them comprised of pyrrolidinyl–camphor–derived bifunctional organocatalysts, where both camphor and pyrrolidine chiral frameworks, connected with an appropriate linker, act in synergy 15–24. All the above mentioned camphor‐derived organocatalysts have been prepared via derivatization of camphor i.e., camphorsulfonic acid at positions 2 and/or 10 (Fig.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and structural elucidation of novel camphor‐derived thioureas

et al. 2012

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Nine novel (+)-camphor-derived thioureas have been prepared. 3-((Dimethylamino)methylene)camphor (2) served as the common precursor for the preparation of both, 2-thiourea 15-20 and 3-thiourea functionalized camphor derivatives 6, 7/7', respectively. Starting from 2, the latter were prepared in two or three steps whereas the former in five steps, respectively. Configuration of all novel compounds has been meticulously determined using NMR techniques and/or single crystal X-ray crystallography.

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“…1). [27][28][29][30][31][32][33][34][35][36] To the best of our knowledge, we could not find any 3,5bis(trifluoromethyl)phenyl thiourea-derived bifunctional organocatalysts with camphor as the exclusive chiral framework. Considering camphor's vast potential for chemical manipulation and our previous experiences with monofunctional camphor-derived thioureas prompted us to investigate the possibility to prepare novel bifunctional thiourea camphor derivatives, preferably in a stereo-divergent synthesis.…”

Section: Introductionmentioning

confidence: 85%

“…Concerning the camphor‐derived noncovalent organocatalysts, the vast majority represent the pyrrolidinyl–camphor‐derived bifunctional organocatalysts, where both camphor and pyrrolidine chiral frameworks, connected with an appropriate linker, act in synergy (Fig. ) …”

Section: Introductionmentioning

confidence: 99%

Synthesis of 2‐(3‐(3,5‐bis(trifluoromethyl)phenyl)thioureido)‐3‐((dimethylamino)methyl)camphor organocatalysts

et al. 2012

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In a stereo-divergent synthesis, three novel camphor-derived bifunctional thiourea organocatalysts 7-9 have been prepared in five steps starting from (+)-camphor. In addition, borneol-derived bifunctional thiourea organocatalysts 19/19' have been prepared in three steps from (1S)-(+)-camphorquinone. Novel organocatalysts 7-9, 19/19' have been evaluated in a model reaction of Michael addition of dimethyl malonate to trans-β-nitrostyrene with low to moderate enantioselectivities (20%-60% ee). Configuration of all novel compounds has been meticulously determined using nuclear magnetic resonance (NMR) techniques.

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Camphor-10-sulfonamide-based prolinamide organocatalyst for the direct intermolecular aldol reaction between ketones and aromatic aldehydes

Cited by 28 publications

References 65 publications

Organocatalyzed Aldol Reactions

Organocatalyzed Aldol Reactions

Synthesis and structural elucidation of novel camphor‐derived thioureas

Synthesis of 2‐(3‐(3,5‐bis(trifluoromethyl)phenyl)thioureido)‐3‐((dimethylamino)methyl)camphor organocatalysts

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