Controlled Heterocyclization/Cross-Coupling Domino Reaction of β,γ-Allendiols and α-Allenic Esters: Method and Mechanistic Insight for the Preparation of Functionalized Buta-1,3-dienyl Dihydropyrans

Palladium-Catalyzed [2+3] Cycloaddition/Cross-Coupling Reaction: Z/E and Diastereoselective Synthesis of Dendralene-Functionalized Dihydrofurans

Herein, we describe a Pd-catalyzed [2+3] cycloaddition/cross-coupling reaction of allenyl acetates for the Z/E selective and diastereoselective synthesis of dendralene-functionalized dihydrofurans. Remarkably, mechanistic studies show the formation of an epoxide from a carbonyl bond via cycloaddition, which is practically and mechanistically significant for the construction of other bioactive heterocyclic epoxides. This research also revealed the utility and potential of allenic esters as C2 synthons and 1,2-biselectrophiles in cycloaddition reactions.

Palladium-catalyzed intermolecular [4 + 2] formal cycloaddition with (Z)-3-iodo allylic nucleophiles and allenamides

A highly chemo- and regioselective [4 + 2] formal cycloaddition of (Z)-3-iodo allylic nucleophiles and allenamides catalyzed by palladium is reported. The methodology proceeds under mild reaction conditions and is tolerant of alkyl and aryl functional groups. The SN2' substitution at the proximal C[double bond, length as m-dash]C bond performed against the Heck or SN2 pathway delivered a variety of 2-amino-dihydropyrans and 2-amino-tetrahydropiperidines in moderate to satisfactory yields. The [4 + 2] formal cycloaddition derivatives are convertible to interesting scaffolds 2,6,7,7a-tetrahydropyrano[2,3-b]pyrrole and 2,6,7,7a-tetrahydro-1H-pyrrolo[2,3-b]pyridine derivatives via ring-closing metathesis (RCM) with Grubbs catalyst II.

Palladium-catalyzed [3+2] annulation of allenyl carbinol acetates with C,N-cyclic azomethine imines

Palladium-catalyzed [3+2] annulation of allenic esters with azomethine imines affording biologically interesting tetrahydropyrazoloisoquinoline derivatives.

Pd-Catalyzed kinetic resolution of cyclic enol ethers. An enantioselective route to functionalised pyrans

Functionalised cyclic enol ethers can be recovered with high levels of enantiocontrol after an asymmetric catalytic [1,3]-rearrangement reaction. These compounds can be further elaborated to a series of carbo- and heterocyclic products in good yield and with excellent levels of stereocontrol.

Palladium-catalysed inter- and intramolecular formation of C–O bonds from allenes

This review highlights the Pd-catalysed formation of a C–O bond from allenes via the inter- or intramolecular reaction.