Pyrrolidinyl–camphor derivatives have been proven to be efficient organocatalysts for enantioselective conjugate addition of ketones to alkylidene malonates, affording high chemical yields (up to 95 %) of the corresponding products with high to excellent levels of diastereoselectivity (up to >99:1 dr) and enantioselectivity (up to 96 % ee) under solvent‐free reaction conditions at ambient temperature.

Practical and convenient synthetic routes have been developed for the synthesis of a new class of pyrrolidinyl-camphor derivatives (7 a-h). These novel compounds were screened as catalysts for the direct Michael addition of symmetrical alpha,alpha-disubstituted aldehydes to beta-nitroalkenes. When this asymmetric transformation was catalyzed by organocatalyst 7 f, the desired Michael adducts were obtained in high chemical yields, with high to excellent stereoselectivities (up to 98:2 diastereomeric ratio (d.r.) and 99 % enantiomeric excess (ee)). The scope of the catalytic system was expanded to encompass various aldehydes and ketones as the donor sources. The synthetic application was demonstrated by the synthesis of a tetrasubstituted-cyclohexane derivative from (S)-citronellal, with high stereoselectivity.

A novel pyrrolidine-camphor organocatalyst 3 was designed, synthesized and proven to be an efficient catalyst for the asymmetric Michael reaction. Treatment of a,a-disubstituted aldehydes with b-nitroalkenes in the presence of 20 mol% organocatalyst 3 and 20 mol% benzoic acid under solvent-free conditions provided the desired Michael product possessing an all-carbon quaternary center with high chemical yields (up to 99% yield) and high levels of enantioselectivities (up to 95% ee).Keywords: asymmetric catalysis; Michael reaction; b-nitroalkenes; quaternary carbon centers; solventfree reaction Remarkable advances have been realized in the use of small privileged organic molecules to catalyze asymmetric reactions. The development of organocatalysts in asymmetric reaction has attracted much attention in recent years as organocatalysts are generally non-toxic, highly efficient and selective, environmentally friendly, and stable under aerobic and aqueous reaction conditions. [1,2] The Michael reaction is one of the most efficient and powerful atom-economic carbon-carbon bond forming reactions in organic chemistry [3] and, therefore, developing enantioselective Michael reactions has been the focus of many organic chemists for decades.[4] Since the pioneering works of organocatalysts, many methods have been developed for the direct asymmetric Michael addition of unmodified aldehydes/ketones with nitroalkenes to produce enantiomerically enriched nitroalkanes. [5] The synthesis of quaternary stereogenic centers is considered a challenging task in organic synthesis [6] and there has been only a few reports on the use of a, a-disubstituted aldehydes.[7] The use of an a,a-disubstituted aldehyde donor should directly produce a Michael product with an all-carbon quaternary center.Most recently, many research groups have independently demonstrated that brine and water are good reaction media for asymmetric Michael reactions of aldehydes and ketones with nitroolefins. [8] Performing organic reactions in aqueous medium is one of the most fundamental and challenging goals and considerable progress has been made in recent years.[9] On the other hand, solvent-free condi-A C H T U N G T R E N N U N G tions, [5k,7a,10] have proved to be very effective in many reaction types due to the intimacy of the reactants. Recently, we have designed and synthesized camphorcontaining thiourea derivatives, as organocatalysts for the asymmetric aldol reaction on water.[11] In continuation of our research interest, we herein, report an eco-friendly process for the direct asymmetric Michael reaction of a,a-disubstituted aldehydes with bnitroalkene acceptors. The novel pyrrolidine-based camphor derivative serves as an efficient bifunctional organocatalyst to catalyze the reaction and provide Michael products possessing an all-carbon quaternary center under solvent-free conditions. High levels of chemical yields and enantioselectivities were generally achieved (up to 99% chemical yield and 95% ee).The design and synthesis of highly stereos...

Remarkable reaction rate and excellent enantioselective direct α‐amination of unmodified aldehydes with various azodicarboxylates was catalyzed by pyrrolidinylcamphor organocatalyst 2a (5 mol‐%) to provide the desired aminated products with excellent chemical yields and high to excellent levels of enantioselectivity (up to >99 % ee) at 0 °C in CH2Cl2.

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