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A facile in situ formed primary amine-imine organocatalyst was developed in the asymmetric Michael addition of substituted 4-hydroxycoumarins to cyclic enones. A series of optically active polycyclic coumarin derivatives were obtained in high yields with excellent enantioselectivities up to 97% ee.Coumarin derivatives are distributed in a large number of natural products and are commonly used as versatile intermediates in natural product synthesis. 1 Modification of this class of compound has been of great interest to chemists due to their various biological activities to antimalarial, anticoagulant, and anti-HIV activities, etc. 2 Although most of coumarin derivatives are currently prescribed as the racemate, activity and metabolism are markedly dissimilar for the two enantiomers. 3 Therefore, efficient asymmetric syntheses of coumarins are of longstanding interest. 4 Organocatalysis has proven itself a valuable strategy in the preparation of the synthesis of optically active coumarins 5 since Jørgensen reported a onestep synthesis of enantiomerically pure warfarin in 2003. 6 They presented the first example of an imidazolidine organocatalyst promoted asymmetric Michael reaction of coumarin and R,β-unsaturated ketones. 7 Chin and Chen

Optically active a-alkylidene-b-amino carbonyl compounds and their derivatives are highly valuable building blocks, which are widely applied in the synthesis of medicinally relevant compounds as well as complex natural products.[1] Therefore, the development of efficient methods for the synthesis of these multifunctional compounds is currently of particular significance. Giving access to valuable compounds and structural complexity, the aza-Morita-BaylisHillman (aza-MBH) reaction provides one of the most direct and versatile methods to these compounds.[2] However, the aza-MBH reaction remains to be restricted in enantiocontrol and substrate scope; the nucleophilic catalysts typically utilized in aza-MBH reactions may induce product racemization.[3] Furthermore, the tosyl groups commonly used as activating groups for the poorly reactive azomethine in the aza-MBH adducts were hard to remove, [4] which limited the application of amino adducts in organic synthesis.Compared with the aza-MBH reaction, the substitution of MBH carbonates with nitrogen nucleophiles is another straightforward strategy to the synthesis of a-methylene-bamino carbonyl compounds through a direct CÀN bond formation reaction.[5] Recently, the asymmetric substitution of MBH carbonates has been established as an effective protocol in C À C bond, [6] C À O bond, [7] C À P bond [8] formation reactions and cycloaddition reactions [9] with high enantioselectivities for a broad range of substrates; however, the asymmetric amination progress was not fruitful. Cyclic imide such as phthalimide was usually employed as the nitrogen nucleophile in this procedure; however, the enantioselectivities of most reported reactions were low to moderate. Searching more suitable nitrogen nucleophiles to achieve higher enantioselectivities and unprotected a-methylene-bamino esters through a simple operation is still a highly desirable goal.The smallest nitrogen nucleophile, ammonia, is theoretically the optimal nitrogen nucleophile, concerning atom economy, [10] but its volatile nature, high reactivity and toxicity makes it difficult to work with in catalytic systems. Benzophenone imine, which is industrially produced by condensation of benzophenone and ammonia, [11] has previously been shown to be an appropriate ammonia equivalent in the asymmetric aza-Michael addition reaction of nitroalkenes reported by Jørgensen.[12] The unprotected b-amino nitro compounds were obtained in good yields and enantioselectivities, and the ammonia carrier benzophenone could be recovered and reused in the preparation of the starting benzophenone imine. Inspired by this elegant progress, and continuing our interest in chiral CÀX (X= N, O, S, Se) bond formation reactions, [13] herein we report the organocatalytic asymmetric allylic amination reaction of MBH carbonates with benzophenone imine. High enantioselectivities (up to 99 % enantiomeric excess (ee)) were achieved for a wide range of MBH carbonates; the optically pure unprotected a-methylene-b-amino esters were easily obtained by a o...