Furan Synthesis via a Tandem 1,2-Acyloxy Migration/[3 + 2] Cycloaddition/Aromatization of Enol Ether-Tethered Propargylic Esters.

An effective method for the synthesis of furans is developed via a tandem 1,2-acyloxy migration/intramolecular [3 + 2] cycloaddition/aromatization of enol ether-tethered propargylic esters. The reaction exhibits excellent functional group tolerance, broad substrate scope, and excellent chemoselectivity. The isolation of dihydrofuran intermediates in some cases gives more insight into the [3 + 2] cycloisomerization process.

Access to Fully Substituted Dihydroindazoles Via Hexadehydro-Diels-Alder/[3 + 2] Cycloaddition.

A cascade hexadehydro-Diels-Alder (HDDA)/[3 + 2] cycloaddition reaction between tetrayne and N,N'-cyclic acylhydrazone is described. This strategy allows the efficient construction of fully substituted 2,3-dihydro-1H-indazole scaffolds which have insecticidal activity against the third instar larvae of Mythimna separata.

Silver Catalyzed Decarbonylative [3 + 2] Cycloaddition of Cyclobutenediones and Formamides.

As an important moiety in natural products, N,O-acetal has attracted wide attention in the past few years. An efficient method to construct N,O-acetal has been developed. Using silver catalyst, cyclobutenediones were smoothly converted to the corresponding γ-aminobutenolides in the presence of formamides, in which cyclobutenediones likely proceed with a key decarbonylative [3 + 2] cycloaddition process. In this way, a series of products with varied substituents were isolated in moderate yield and fully characterized.

GaCl3-Catalyzed C-H Cyanation of Indoles with N-Cyanosuccinimide.

An efficient GaCl3-catalyzed direct cyanation of indoles and pyrroles using bench-stable electrophilic cyanating agent N-cyanosuccinimide was achieved and afforded 3-cyanoindoles and 2-cyanopyrroles in good yields and excellent regioselectivities. Notably, this protocol exhibited high reactivity for unprotected indoles and was applicable to a broad range of indole and pyrrole substrates.

Asymmetric Total Synthesis of Four Stereoisomers of the Sex Pheromone of the Western Corn Rootworm.

A convergent synthesis of four stereoisomers of the sex pheromone of the western corn rootworm (8-methyldecan-2-yl propionate, 1) from commercially available chiral starting materials is reported. The key step was Julia-Kocienski olefination between chiral BT-sulfone and chiral aldehyde. This synthetic route provided the four stereoisomers of 1 in 24-29% total yield via a six-step sequence. The simple scale-up strategy provides a new way to achieve the asymmetric synthesis of the sex pheromone.

Palladium(0)-catalyzed Heck reaction/C-H activation/amination sequence with diaziridinone: a facile approach to indolines.

Indolines are important moieties present in various biologically significant molecules and have attracted considerable attention in synthetic chemistry. This paper describes a Heck reaction/C-H activation/amination sequence for forming indolines using di-tert-butyldiaziridinone. The reaction process likely proceeds via a pallada(II)cycle, which is converted into an indoline by oxidative addition to the diaziridinone and two subsequent C-N bond formations.

Asymmetric Total Synthesis of (+)-Chuanxiongnolide L1 via a Stereoselective Oxidative Dearomatization/Diels-Alder Strategy.

The first asymmetric total synthesis of chuanxiongnolide L1 was achieved in 16 steps and 1.9% overall yield by employing a bioinspired chiral auxiliary strategy. The key steps involving asymmetric oxidative dearomatization of chiral amino ether and subsequent asymmetric Diels-Alder reaction of the resulting masked chiral ortho-benzoquinone were adopted.

Stereoselective synthesis of fused spiroindolines via tandem Mannich/intramolecular aminal formation.

A novel tandem Mannich/intramolecular aminal formation between tryptamines and salicylaldehydes was reported. This strategy provides a promising approach for the stereoselective synthesis of a range of complex fused spiroindolines, which bear a highly congested contiguous spiro quaternary center and two tertiary stereocenters, in a highly economical and effective fashion.

Synthesis of the tetracyclic core (ABCE rings) of daphenylline.

A concise synthesis of the tetracyclic core (ABCE rings) of daphenylline has been accomplished involving a benzobicyclo[3.3.1] lactam as the key intermediate. This bridged bicyclic intermediate was efficiently constructed via a Brønsted acid promoted intramolecular Friedel-Crafts type Michael addition of a δ-benzyl α,ß-unsaturated δ-lactam.

Asymmetric total synthesis of cladosporin and isocladosporin.

The first asymmetric total syntheses of cladosporin and isocladosporin were accomplished in 8 steps with 8% overall yield and 10 steps with 26% overall yield, respectively. The relative configuration of isocladosporin was determined via this total synthesis.

Synthesis of the [6.6.7.5] Tetracyclic Core of Calyciphylline N via a Boc-Mediated Oxidative Dearomatization/Diels-Alder Approach.

A sequential process involving Boc-mediated oxidative dearomatization and inter/intramolecular Diels-Alder reaction was investigated. Based on an intermolecular Diels-Alder reaction and subsequently a radical 7-endo-trig type cyclization, the [6.6.7.5] tetracyclic core of Calyciphylline N was assembled.

PtI2-catalyzed tandem 3,3-rearrangement/Nazarov reaction of arylpropargylic esters: synthesis of indanone derivatives.

An efficient PtI(2)-catalyzed tandem reaction of arylpropargylic esters, involving 3,3-rearrangement and Nazarov reaction, has been developed to produce 3-substituted and 3,3-disubstituted indanone derivatives. This approach provided a pathway to the synthesis of indanone skeletons in natural products.

Pt-catalyzed tandem 1,2-acyloxy migration/intramolecular [3 + 2] cycloaddition of enynyl esters.

A platinum-catalyzed tandem reaction involving enynyl ester isomerization and subsequent intramolecular [3 + 2] cyclization has been developed. This strategy provides an efficient approach to five-, six-, or seven-membered cyclic polyfunctional compounds.

Biomimetic total synthesis of (+)-chabranol.

A concise, biomimetic total synthesis of the unprecedented terpenoid skeleton (+)-chabraol has been accomplished via 6 steps from the chiral epoxide 7, involving an intramolecular Prins double cyclization to yield the bicyclo[2.2.1] core of the natural product as the key step. The absolute configuration of natural chabranol was also designated through the first asymmetric total synthesis.

Total Synthesis of Caesalpinnone A.

Total synthesis of caesalpinnone A was achieved in 12 steps starting from resorcinol. Key features of the synthesis include BINOL-phosphoric acid catalyzed [4 + 2] cycloaddition, trans-selective nucleophilic substitution, deallylation/oxa-Michael addition cascade, and late-stage photo-Fries rearrangement.

Dearomatization of Indole via Intramolecular [3 + 2] Cycloaddition: Access to the Pentacyclic Skeleton of Strychons Alkaloids.

An efficient method to build various multisubstituted polycyclic indoline-annulated normal to medium-size rings through dearomatization of indole via a tandem 1,2-acyloxy migration/intramolecular [3 + 2] cycloaddition process is described. The pentacyclic skeleton of strychnine could be synthesized via this tandem cycloaddition and a further Mannich reaction. This approach would provide a novel strategy to the synthesis of strychons alkaloids.

Pd(0)-catalyzed sequential C-N bond formation via allylic and aromatic C-H amination of α-methylstyrenes with diaziridinone.

A novel Pd(0)-catalyzed sequential C-N bond formation process via allylic and aromatic C-H amination of α-methylstyrenes with di-tert-butyldiaziridinone, giving spirocyclic indolines in good yields, is described. Four C-N bonds and one spiro quaternary carbon are generated in a single operation.

Tandem oxidative dearomatization/intramolecular Diels-Alder reaction for construction of the tricyclic core of palhinine A.

A concise construction of the 6/6/5 tricyclic core of Lycopodium alkaloid palhinine A (1) has been accomplished. The developed synthetic strategy featured a tandem oxidative dearomatization/intramolecular Diels-Alder reaction to construct C/D rings and an intramolecular 5-exo-trig radical cyclization to install the B ring of palhinine A (1). The developed approach paves the way for the total synthesis of palhinine A (1).

Au-catalyzed piperidine synthesis via tandem acyloxy migration/intramolecular [3 + 2] cycloaddition of enynyl esters.

An Au-catalyzed tandem protocol involving enynyl ester isomerization and subsequent intramolecular [3 + 2] cyclization has been developed. This strategy provides an efficient approach for the synthesis of polyfunctional piperidines, which are subunits of many bioactive molecules.