Search

We report a Brønsted acid‐catalyzed synthesis of tetrasubstituted allenyl compounds decorated with heterocyclic sulfenyl group. The reaction proceeds readily from available propargylic alcohols in the presence of pentacarboxycyclopenatadienes (PCCPs) as organocatalysts. The developed strategy provides tetrasubstituted allene derivatives in high yields (from 55 to 98 %) and under mild reaction conditions. [ABSTRACT FROM AUTHOR]

Over the last ten years, the combination of organocatalysis with transition metal (TM) catalysis has become one of the most important toolboxes used for synthesizing optically pure compounds containing chiral quaternary centers, including spiro heterocyclic molecules. The dominant method in the enantioselective synthesis of spiro heterocyclic compounds based on synergistic catalysis includes chiral aminocatalysis and NHC catalysis, as already established covalent organocatalytic strategies. Another area of organocatalysis widely combined with TM catalysis producing enantiomerically enriched spiro heterocyclic compounds is non‐covalent catalysis, dominated by chiral phosphoric acids, thiourea, and squaramide derivatives. This review article aims to summarize enantioselective methods used for constructing spirocyclic heterocycles based on a combination of organocatalysis and transition metal catalysis. [ABSTRACT FROM AUTHOR]

An organocatalytic asymmetric domino Michael/α‐alkylation reaction between enals and non‐stabilized alkyl halides has been developed. Chiral secondary amine catalyzed cyclization reaction of 1‐bromo‐3‐nitropropane with α,β‐unsaturated aldehydes provides 1,2,3‐trisubstituted cyclopentane carbaldehydes with high diastereo‐ (dr up to 8 : 1) and enantioselectivities (ee up to 96 %). [ABSTRACT FROM AUTHOR]

The present study reports the asymmetric cyclization of enals with vinylcyclopropane azlactones efficiently catalyzed by the combination of achiral Pd(0) complexes and chiral secondary amines. Corresponding spirocyclic azlactones were produced in high yields with moderate diastereoselectivities and excellent enantioselectivities. This protocol provides an efficient and easily-performed route to spirocyclic scaffolds, and densely functionalized cyclopentanes containing quaternary carbon centers. [ABSTRACT FROM AUTHOR]

The enantioselective amination of Morita–Baylis–Hillman carbonates with silylated derivatives of tert-butylhydroxycarbamates using β-isocupreidine as an organocatalyst was investigated. The corresponding products were obtained in good yields with high enantioselectivities. The scope and limitations of the reported protocol were explored, and representative transformations of the adducts toward heterocyclic compounds were highlighted. [ABSTRACT FROM AUTHOR]

Abstract: Organocatalytic alkynylation of nucleophilic fluorocarbons using hypervalent iodine compounds under cinchona-based catalysis, namely using O-allyl N-anthracenyl cinchona alkaloid derivative II, is described. The reaction gives the final fluoro-propargyl compounds in good to excellent yields (up to 91%) and with moderate to low enantioselectivity (up to 61% ee). The reaction represents the first example of the use of hypervalent iodine compounds for the construction of fluorinated compounds and opens access to the preparation of biologically attractive compounds such as 1,2,3-triazoles. [Copyright &y& Elsevier]

Abstract: The highly enantioselective organocatalytic α-selenylation reaction of aldehydes using a hypervalent iodine compound as an oxidative agent from commercially available phenyl diselenide under mild oxidative conditions is described. This transformation affords α-selenyl aldehydes in good yields and with excellent enantioselectivities. By using hypervalent iodine compounds, it opens up a suitable and alternative way for the preparation of biologically active building blocks such as β-hydroxy alcohols, α-amino acids, and α-hydroxy esters. [Copyright &y& Elsevier]

Herein, we report the first chiral phosphoric acid (CPA)-catalyzed asymmetric addition of α-fluoro(phenylsulfonyl)methane (FSM) derivatives to in situ generated cyclic N-acyliminium. This process enables metal-free expeditious access to sulfone and fluorine incorporating contiguous all substituted quaternary stereocenters ingrained in biorelevant isoindolinones in excellent stereoselectivities (up to 99% ee and up to 50 : 1 dr). [ABSTRACT FROM AUTHOR]

An organocatalytic asymmetric allylic amination of Morita- Baylis-Hillman carbonates with aromatic amines in the presence of ß- isocupreidine is described. Chiral allylic amines were obtained in almost quantitative yields (90-96%) with moderate enantioselectivity. Recrystallization afforded products in good yields (45-73%) and high optical purity (82-99% ee). This method provides a facile and efficient route to obtain optically active ß-lactams, including the building block of the cholesterol-lowering drug Ezetimibe. [ABSTRACT FROM AUTHOR]

The successful α-selenylation methodology is also applicable to β-keto esters like (V). [ABSTRACT FROM AUTHOR]

The alkynylation of nucleophilic fluorocarbons (II) with hypervalent iodine compound (I) is developed using a cinchona alkaloid derivative as catalyst. [ABSTRACT FROM AUTHOR]

Review: 41 refs. [ABSTRACT FROM AUTHOR]

Abstract: A highly enantioselective organocatalytic fluoromalonate addition to α,β-unsaturated aldehydes is reported. The reaction is catalyzed by simple and commercially available secondary amines, affording the corresponding 1,4-adducts with high yields and enantioselectivities. [Copyright &y& Elsevier]