[reaction: see text] A sequential acylation-intramolecular cyclopropanation reaction takes place upon treatment of a series of tetraalkylammonium acylchromates with beta,gamma-unsaturated acyl chlorides at -10 degrees C. The reaction leads to 2-oxabicyclo[3.1.0]hexan-3-ones with exo selectivity in good yields. The diastereoselectivity of the reaction allows the preparation of cis-divinyl cyclopropanes, which evolve via Cope sigmatropic reaction toward cycloheptadiene derivatives. Furthermore, the aromatic Cope rearrangement of a series of cis-aryl vinyl cyclopropanes prepared by means of this methodology has been studied.

A cholic acid-based bis-primary amine is capable of promoting the insertion of CO2 into epoxides with the cooperative aid of an iodide anion. This framework is transformed in situ into a bis-carbamic acid. The latter is the active catalytic species, operating through H-bonding interactions. Our system works with complete atom economy, under solvent-free, metal-free, and mild conditions. Also, it can be recycled.

A novel tripodal carbamate-based steroidal architecture works as an efficient catalyst on the Michael-type addition reaction between dimethyl malonate and nitrostyrene. Its action mode has been disclosed by quantum chemical calculations. It comprises the preorganization and confinement of the reagents within the active chiral cavity of the steroid, which are held together by means of cooperative Hbond contacts. Organocatalysis consists in the acceleration of chemical reactions employing small organic frameworks typically assembled from C, H, O, N, S and P atoms. [1] Some privileged structures have been widely used for building up asymmetric organocatalysts: derivatives of 1,2-diamines, 1, BINOL, 2, proline or other natural amino acids, 3, and cinchona alkaloids, 4 (Figure 1). Alternative chiral scaffolds are extensively sought after. Herein we describe the ability of a steroidal platform, based on cholic acid, 5, to work as an enantioselective organocatalyst that makes use of cooperative weak H-bonding interactions.

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