Practical Approach to α- or γ-Heterosubstituted Enoic Acids

Catalyst- and base-free visible light-enabled radical relay trihalomethylation/functional group-migration/carbonylation with CX3SO2Cl

Herein, we report a visible light-enabled radical trihalomethylation/cyano-migration/carbonylation cascade reaction of 2-hydroxy-2-hex-5-enenitrile with CX3SO2Cl as the CX3-source (X = F, Cl) to obtain 5-oxo-2-(2,2,2-trihaloethyl)pentanenitrile compounds in the absence of a photocatalyst, transition metal and base. This reaction system is also effective to convert (benzo[d]thiazol-2-yl)-pent-4-enol to the corresponding 4-(benzo[d]thiazol-2-yl)-6,6,6-trihalo-hexanone products. These reactions occur under mild conditions, tolerate a wide range of functional groups, and provide alternative approaches for the 1,2-bifunctionalization reaction of unactivated olefins.

Penicitone: Structural Reassignment of a Proposed Natural Product Acid Chloride

The proposed structure for the natural product penicitone, which contained a chemically improbable acid chloride functional group, was reassigned to a more probable structure using a combination of chemical knowledge, computer-assisted structure elucidation, and DFT methods.

Pd-catalyzed synthesis of 1-(hetero)aryl-2,2,2-trichloroethanols using chloral hydrate and (hetero)arylboroxines

1-(Hetero)aryl-2,2,2-trichloroethanols are useful key intermediates for the synthesis of various bioactive compounds. Herein, we describe N-heterocyclic carbene (NHC)-coordinated cyclometallated palladium complex (CYP)-catalyzed (hetero)aryl addition of chloral hydrate using (hetero)arylboroxines, providing a new approach to 1-(hetero)aryl-2,2,2-trichloroethanols. Notably, PhS-IPent-CYP which coordinated the bulky yet flexible 2,6-di(pentan-3-yl)aniline (IPent)-based NHC showed good catalytic activities and promoted the transformation in 24-97% yields.

Recent approaches towards one-carbon homologation-functionalization of aldehydes

One-carbon homologation-functionalization in organic synthesis is a quite challenging and difficult task in terms of atom economy, ease of reaction, selectivity and number of steps involved. Due to the reactivity associated with most classes of carbonyls, these groups have always attracted a great deal of attention from synthetic chemists to transform them into various functionalities. In this context various researchers developed new methods for one-carbon extension-functionalization of carbonyls that serve as effective synthetic methodologies and are widely used in target-oriented and natural product synthesis. On account of the vast applicability associated with these transformations, herein we seek to summarize and highlight the important synthetic achievements in this advancing arena for various one-carbon homologation cum functionalization reactions of aldehydes and deep dive into some modern approaches adopted by organic chemists.

Elodeoidins A–H, acylphloroglucinol meroterpenoids possessing diverse rearranged skeletons from Hypericum elodeoides

Inspired by the biosynthetic fragment (9), the first example of rearranged dimethylated acylphloroglucinol and monoterpene adducts, elodeoidins A–H (1–8) representing four skeletons and two rearranged pathways were authenticated from H. elodeoides.

Two New Geranylated Biphenyl Esters From Artocarpus altilis

Two new geranylated biphenyl esters, 2,3′,4,4′-tetrahydroxy-3-geranyl-5-carboxyethyl-biphenyl methyl ester (1), 2,3′,4,4′-tetrahydroxy-3-geranyl-5-carboxymethyl-biphenyl methyl ester (2), together with 4 known compounds were isolated from the methanol extract of the leaves of Artocarpus altilis. Their structures were established by spectroscopic means and by comparison with literature data. Compound 1 possessed moderate cytotoxicity toward MDA-MB-231 (a breast carcinoma cell line) with a half-maximal inhibitory concentration value of 30 µM and inhibited the growth of 8 bacteria, including gram-negative and gram-positive organisms, but was inactive against fungi.

Strategies for the synthesis of spiropiperidines - a review of the last 10 years

Spiropiperidines have gained in popularity in drug discovery programmes as medicinal chemists explore new areas of three-dimensional chemical space. This review focuses on the methodology used for the construction of 2-, 3- and 4-spiropiperidines, covering the literature from the last 10 years. It classifies the synthesis of each of the types of spiropiperidine by synthetic strategy: the formation of the spiro-ring on a preformed piperidine ring, and the formation of the piperidine ring on a preformed carbo- or heterocyclic ring. While 3- and 4-spiropiperidines are predominantly synthesised for drug discovery projects, 2-spiropiperidines are synthesised en route to natural products. The lack of 2-spiropiperidines in drug discovery is presumably due to limited general procedures for their synthesis.

Enantioselective total synthesis of decytospolide A and decytospolide B using an Achmatowicz reaction

Enantioselective syntheses of decytospolide A and decytospolide B are described here. The current synthesis highlights an Achmatowicz rearrangement of an optically active furanyl alcohol followed by reduction of the resulting dihydropyranone hemiacetal with BF3·OEt2 and Et3SiH to provide the saturated tetrahydropyranyl alcohol directly. This reduction was investigated with a variety of other Lewis acids. The synthesis also features Noyori asymmetric transfer hydrogenation and Friedel-Crafts acylation. Overall, the synthesis provides ready access to the natural products and may be useful in the preparation of bioactive derivatives.

Mg(OMe)2 promoted allylic isomerization of γ-hydroxy-α,β-alkenoic esters to synthesize γ-ketone esters

This work concerns the Mg(OMe)₂ promoted allylic isomerization of γ-hydroxy-α,β-alkenoic esters with TMEDA as an additive. The isomerization proceeded under mild conditions and afforded γ-keto esters in high yield (up to 96%) within 2 h. Both (Z)- and (E)-γ-hydroxy-α,β-alkenoic esters were tolerated under the reaction conditions. This transformation involves the in situ formation of a dienolate intermediate from the easily accessible γ-hydroxy-α,β-alkenoic ester. The in situ generated dienolate can react with benzaldehyde and undergo a practical, useful tandem allylic isomerization-Aldol reaction to afford more functionalized compounds.

Synthesis of 1- and 4-substituted piperazin-2-ones via Jocic-type reactions with N-substituted diamines

Enantiomerically-enriched trichloromethyl-containing alcohols are transformed regioselectively into enantiomerically-enriched 1-substituted piperazinones by modified Jocic reactions.

One-pot in situ formation and reaction of trimethyl(trichloromethyl)silane: application to the synthesis of 2,2,2-trichloromethylcarbinols

2,2,2-Trichloromethylcarbinols are 1 are valuable synthetic intermediates with a multitude of uses. A scalable procedure for the synthesis of TMS-protected-2,2,2-trichloromethylcarbinols and 2,2,2-trichloromethylcarbinols 1 was developed that employs the in situ generation and reaction of trimethyl(trichloromethyl)silane (CCl(3)-TMS). The procedure avoids the exposure of the carbonyl compounds to the strongly basic conditions typically used for this transformation and also avoids isolation of the difficult-to-handle CCl(3)-TMS. This procedure was applied to diastereoselective trichloromethyl additions to 2-substituted 4-piperidinones and to reactions with a variety of structurally diverse aldehydes and ketones.

Enantioselective synthesis of schulzeines B and C via a beta-lactone-derived surrogate for bishomoserine aldehyde

Enantioselective syntheses of the glucosidase inhibitors schulzeines B and C were achieved by employing a Pictet-Spengler reaction of a beta-lactone-derived, masked bishomoserine aldehyde. Subsequent Corey-Link reaction unveiled an alpha-azido acid enabling cyclization to the delta-lactam fused tetrahydroisoquinoline. An efficient synthesis of the trisulfate-bearing side chain featured a Noyori hydrogenation and a Sharpless dihydroxylation. An unexpected reaction of a pendant amine during a Corey-Link process opens avenues for the synthesis of proline and related amino acid derivatives.

An expeditious synthesis of 4-hydroxy-2E-nonenal (4-HNE), its dimethyl acetal and of related compounds

The facile one step synthesis of 4-hydroxy-2E-nonenal and its dimethyl acetal via a cross-metathesis reaction between commercially available octen-3-ol and acrolein or its dimethyl acetal is reported. The method was extended to the synthesis of C6 and C12 4-hydroxy-2E-enals, their dimethyl acetal and of the 4-hydroxy-2E-nonenoic acid (4-HNA).