Aminodealkenylation: Ozonolysis and copper catalysis convert C(sp)-C(sp) bonds to C(sp)-N bonds.

Great efforts have been directed toward alkene π bond amination. In contrast, analogous functionalization of the adjacent C(sp)-C(sp) σ bonds is much rarer. Here we report how ozonolysis and copper catalysis under mild reaction conditions enable alkene C(sp)-C(sp) σ bond-rupturing cross-coupling reactions for the construction of new C(sp)-N bonds.

Dealkenylative Alkynylation Using Catalytic Fe and Vitamin C.

In this paper, we report the synthesis of alkyl-tethered alkynes through ozone-mediated and Fe-catalyzed dealkenylative alkynylation of unactivated alkenes in the presence of alkynyl sulfones. This one-pot reaction, which employs a combination of a catalytic Fe salt and l-ascorbic acid, proceeds under mild conditions with good efficiency, high stereoselectivity, and broad functional group compatibility. In contrast to our previous Fe-mediated reductive fragmentation of α-methoxyhydroperoxides, the Fe-catalyzed process was devised through a thorough kinetic analysis of the multiple competing radical (redox) pathways.

Dealkenylative Alkenylation: Formal σ-Bond Metathesis of Olefins.

The dealkenylative alkenylation of alkene C(sp )-C(sp ) bonds has been an unexplored area for C-C bond formation. Herein 64 examples of β-alkylated styrene derivatives, synthesized through the reactions of readily accessible feedstock olefins with β-nitrostyrenes by ozone/Fe -mediated radical substitutions, are reported. These reactions proceed with good efficiencies and high stereoselectivities under mild reaction conditions and tolerate an array of functional groups.

Hydrodealkenylative C(sp)-C(sp) bond fragmentation.

Chemical synthesis typically relies on reactions that generate complexity through elaboration of simple starting materials. Less common are deconstructive strategies toward complexity-particularly those involving carbon-carbon bond scission. Here, we introduce one such transformation: the hydrodealkenylative cleavage of C(sp)-C(sp) bonds, conducted below room temperature, using ozone, an iron salt, and a hydrogen atom donor.

Synthesis of Cyclic β-Silylalkenyl Triflates via an Alkenyl Cation Intermediate.

Trimethylsilylalkyne derivatives are transformed into cyclic β-silylalkenyl triflates through cationic cyclization and subsequent trapping of the alkenyl cation by a triflate anion. β-Silylcyclohexenyl triflates and 3-trimethylsilyl-1,4-dihydronaphth-2-yl triflates are generated efficiently using this methodology. These products provide ready access to substituted cyclohexynes, exemplified by a concise total synthesis of β-apopicropodophyllin.

Stereoselective synthesis of spiro[tetrahydropyran-3,3'-oxindole] derivatives employing Prins cascade strategy.

A variety of aldehydes undergo smooth coupling with 4-hydroxy-N-methyl-2-methylene-N-phenylbutanamide in the presence of BF3·OEt2 under ambient conditions to produce the corresponding spiro-oxindole derivatives in good yields with excellent selectivity. It is an entirely new strategy to construct the spirocycles in a one-pot operation through a Prins cascade process.

Gold-catalyzed domino cycloisomerization/Pictet-Spengler reaction of 2-(4-aminobut-1-yn-1-yl)anilines with aldehydes: synthesis of tetrahydropyrido[4,3-b]indole scaffolds.

A domino cycloisomerization/Pictet-Spengler reaction of 2-(4-aminobut-1-yn-1-yl)aniline with aldehydes has been achieved using a AuIPrCl (5 mol %)/AgSbF(6) (10 mol %) catalytic system to produce the corresponding 1-aryl-N-tosyl-2,3,4,5-tetrahydropyrido[4,3-b] indole derivatives in good yields. This is the first report on the synthesis of tetrahydro pyrido[4,3-b]indole scaffolds through as tandem 5-endo-dig cyclization and Pictect-Spengler reaction.

A domino Knoevenagel hetero-Diels-Alder reaction for the synthesis of polycyclic chromene derivatives and evaluation of their cytotoxicity.

A novel octahydrochromeno[4,3-a]xanthen-1(2H)-one derivatives has been prepared using 10mol% dl-proline in ethanol via a domino Knoevenagel hetero-Diels-Alder reaction of alkene-tethered chromene-3-carboxaldehyde with cyclic 1,3-diketones. This is not only the first example on the preparation of highly diastereoselective pentacyclic chromene derivatives from alkene appended chromene-3-carboxaldehyde in one-pot process at ambient temperature but also preliminary evaluation of the cytotoxic activity of these chromene derivatives. Some of these compounds are found to exhibit potent cytotoxicity against two carcinoma cell lines A549 and B-16.