Efficient Synthesis of Functionalised 4-Hydroxycyclopent-2-en-1-ones by Cyclisation of 1,3-Bis(silyl) Enol Ethers and 1,3-Dicarbonyl Dianions with 1,2-Diketones

α-Iodo-α,β-Unsaturated Ketones as Vicinal Dielectrophiles: Their Reactions with Dinucleophiles Provide New Annulation Protocols for the Formation of Carbo- and Heterocyclic Ring Systems

α-Iodo-α,β-unsaturated ketones such as compound 1 serve as vicinal dielectrophiles and react with a range of dinucleophiles including pentane-2,4-dione and 1,3-indandione to produce [3 + 2]- and [2 + 1]-adducts such as 5 and 38, respectively. [4 + 2]- and [5 + 2]-cycloadducts have been obtained from compound 1 by related means. Preliminary studies reveal that α-iodinated α,β-unsaturated esters can also participate in at least some of these same processes.

An uncommon multicomponent reaction involving nucleophilic heterocyclic carbenes: facile synthesis of fully substituted cyclopentanones

An unprecedented three component reaction involving arylidene oxazolone, enal and NHC, leading to the synthesis of fully substituted cyclopentanone derivatives with three contiguous stereocenters, is reported.

Synthetic versatility of 2-substituted-6-methyl 2,3-dihydropyridinones in the synthesis of polyfunctional piperidine-based compounds and related β amino acid derivatives

Chiral 2-substituted-6-methyl 2,3-dihydropyidinones 9, which can be facilely obtained from an asymmetric vinylogous Mannich reaction (VMR) with 1,3-bis-trimethysily enol ether, were used as versatile intermediates in constructing chiral polyfunctional piperidine-based compounds. The 6-methyl group of such compounds can be conveniently functionalized via alkylation and acylation reactions to provide efficient entries to the synthesis of a variety of chiral multi-substituted piperidine-based compounds. Further elaboration of the corresponding intermediates also provided access to polyfunctional indolizidine-based compounds. These methods were showcased in an asymmetric synthesis of 2,6-di-substituted piperidine compound 13, reported as the key intermediate in the synthesis of (+)-calvine and a natural alkaloid (-)-indolizidine 209D. Furthermore, selective C5 iodination of compound 9 enabled the installation of additional functional groups at this position. Finally, we demonstrated that the oxidative cleavage of 2-substituted-6-methyl-2,3-dihydropyidinones is a practical and efficient method for the enantioselective synthesis of β-amino acids, which can undergo further intra-molecular cyclization to give the corresponding chiral four-membered β-lactam derivatives.

Diastereoselective construction of cyclopent-2-enone-4-ols from aldehydes and 1,2-allenones catalyzed by N-heterocyclic carbene

Cyclopent-2-enone-4-ols have been prepared highly diastereoselectively from readily available aromatic aldehydes and 1,2-allenones catalyzed by N-heterocyclic carbene. Mechanistic studies showed that there are four possible pathways.

Synthesis and Applications of Hajos-Parrish Ketone Isomers

Numerous natural products possess ring systems and functionality for which Hajos-Parrish ketone isomers with a transposed methyl group (termed "iso-Hajos-Parrish ketones") would be of value. However, such building blocks have not been exploited to the same degree as the more typical Hajos-Parrish hydrindane. An efficient three-step synthesis of such materials was fueled by a simple method for the rapid preparation of highly functionalized cyclopentenones, several of which are new chemical entities that would be challenging to access through other approaches. Furthermore, one iso-Hajos-Parrish ketone was converted into two distinct natural product analogues and one natural product. As one indication of the value of these new building blocks, that latter target was obtained in 10 steps, having previously been accessed in 18 steps using the Hajos-Parrish ketone.

Building polyfunctional piperidines: a stereoselective strategy of a three-component Mannich reaction inspired by biosynthesis and applications in the synthesis of natural alkaloids (+)-241D; (−)-241D; isosolenopsin A and (−)-epimyrtine

A stereoselective strategy for building polyfunctional piperidines by a three-component Mannich reaction and applications in the stereoselective synthesis of natural alkaloids.