Pd(II)-Catalyzed Synthesis of Bicyclo[3.2.1] Lactones via Tandem Intramolecular β-C(sp3)-H Olefination and Lactonization of Free Carboxylic Acids

Bicyclo[3.2.1] lactones are chemical scaffolds found in numerous bioactive natural products. Herein, we detail the development of a novel palladium(II)-catalyzed tandem intramolecular β-C(sp³)-H olefination and lactonization reaction that rapidly transforms linear carboxylic acid possessing a tethered olefin into the bicyclo[3.2.1] lactone motif. This transformation features a broad substrate scope, shows excellent functional group compatibility, and can be extended to the preparation of the related seven-membered bicyclo[4.2.1] lactones. Additionally, we demonstrate the synthetic potential of this annulation by constructing the 6,6,5-tricyclic lactone core structure of the meroterpenoid cochlactone A. We anticipate that this compelling reaction may provide a novel synthetic disconnection that can be broadly applied toward the preparation of a variety of bioactive natural products.

The synthesis of indeno[de]isochromene derivatives from arylvinyl epoxides and carbonyl compounds via tandem Nazarov and oxa-Pictet–Spengler cyclizations

The conversion of aryl vinyl epoxides and carbonyl compounds in the presence of a catalytic amount of BF3·OEt2 to indeno[de]isochromenes via tandem Nazarov and oxa-Pictet–Spengler cyclizations is described.

Palladium-catalyzed δ-selective reductive Heck reaction of alkenyl carbonyl compounds with aryl iodides and bromides

A simple, operationally convenient and highly regioselective palladium-catalyzed reductive Heck reaction of alkenyl carbonyl compounds with aryl iodides and bromides has been developed to afford structurally diverse δ-aryl pentanoic acid derivatives.

Synthesis of Benzo[1,4]heterocycles using Palladium Catalyzed Heck Reaction to Vinylogous Carbonates/Carbamates: Unexpected Formation of Indoles via Carbopalladation Intercepted by Nucleopalladation

An efficient protocol for the stereoselective synthesis of benzo[1,4]heterocycles via palladium catalyzed Heck reaction on o-halo-aryl-oxa/thia/aza tethered vinylogous carbonates/carbamates/esters has been developed. Unexpected formation of indoles is observed when unprotected 2-iodoaniline tethered vinylogous carbonates are subjected to the Heck reaction. Mechanistic studies indicate that formation of these indoles is an outcome of the interception of the carbopalladation step by nucleopalladation. The method can be used to gain rapid access to the core skeleton of abacopterin A-C.

Stereoselective synthesis of thiazino[4,3-a]indoles using the thia-Pictet-Spengler reaction of indoles bearing N-tethered thiols and vinylogous thiocarbonates

An inter- as well as intra-molecular thia-Pictet-Spengler cyclization of N-tethered thiols and vinylogous thiocarbonates is described for the stereoselective synthesis of N-fused thiazinoindole derivatives. The strategy is extended to one-pot, sequential Friedel-Crafts alkylation - Pictet-Spengler cyclization and the synthesis of thiazino-oxepino-indole.

Organocatalytic, Enantioselective Synthesis of 1- and 3-Substituted Isochromans via Intramolecular Oxa-Michael Reaction of Alkoxyboronate: Synthesis of (+)-Sonepiprazole

The enantioselective oxa-Michael reaction of alkoxyboronate strategy was demonstrated to provide a new and practical route to enantioriched 1- and 3-substituted isochromans using a chiral bifunctional organocatalyst. Furthermore, this methodology was extended to the enantioselective synthesis of (+)-sonepiprazole, a dopamine receptor antagonist.