Highly Enantioselective Synthesis of Nitrocyclopropanes via Organocatalytic Conjugate Addition of Bromomalonate to α,β-Unsaturated Nitroalkenes

Abstract

Highly enantioselective synthesis of nitrocyclopropanes was achieved via the organocatalytic conjugate addition of dimethyl bromomalonate to nitroalkenes and the consequent intramolecular cyclopropanation. 6'-Demethyl quinine was found to be the efficient catalyst. Excellent enantioselectivities, diastereoselectivities, and good yields were obtained for a variety of aryl or heteroaryl nitroethylenes.

1,3-Dicarbonyl compounds in stereoselective domino and multicomponent reactions

“…108 This cascade is related to the one described previously (see scheme 42) but the activation mode is different since in the present case, the organocatalyst 135 activates the substrates through hydrogen bonding interactions. Recently, an enantioselective Robinson-type annulation catalyzed by two structurally different chiral phosphoric acids has been described (Scheme 52).…”

Stereoselective synthesis of functionalised cyclopropanes from nitroalkenes via an organocatalysed Michael-initiated ring-closure approach

“…This simple approach has been recently improved by Yan using 6 0 -demethyl-quinine as the catalyst and dimethyl bromomalonate as the nucleophile. 8 In this case, DABCO in DMF rather than DBU in less environmentally friendly hexamethylphosphoramide (HMPA) was found to be more effective conditions for the ring closure. Excellent diastereo-and enantioselectivity and good yields of product were obtained for a variety of aryl and heteroaromatic nitroalkenes.…”

Cyclopropanation of 5-(1-Bromo-2-phenyl-vinyl)-3-methyl-4-nitro-isoxazoles under Phase Transfer Catalysis (PTC) Conditions

“…Pioneered by Aggarwal and Dai, [18][19][20][21][22] the affirmation of organocatalysis [23,24] delivered a number of high enantioselective cyclopropanation protocols, for example those reported by Gaunt [25][26][27][28][29] and MacMillan [30]. Recently, Michael Initiated Ring Closing (MIRC) processes appeared in the literature [31][32][33][34][35][36][37][38][39][40], particularly by W. Wang, [33] Cordova, [34] Y. Wang, [38] Yan, [39] and Tiecco. [40] These methodologies gave densely substituted cyclopropanes in good yields and good to excellent diastereo-and enantio-selectivity.…”