Elsevier

Tetrahedron

Volume 57, Issue 7, 11 February 2001, Pages 1347-1359
Tetrahedron

Palladium catalysed queuing processes. Part 1: Termolecular cyclization–anion capture employing carbon monoxide as a relay switch and hydride, organotin(IV) or boron reagents

https://doi.org/10.1016/S0040-4020(00)01103-0Get rights and content

Abstract

The concept of relay switch reactants, which substantially enhance the scope of our cyclization–anion capture methodology, is introduced and exemplified by a wide variety of catalytic cyclization–carbonylation–anion capture processes employing hydride, organostannanes and NaBPh4 as anion capture agents. Mono- and bis-cyclization processes forming 5- and 6-membered rings are described, all of which employ CO at atmospheric pressure. Cyclocarboformylation processes provide interesting analogues of hydroformylation.

Section snippets

Background

In current studies we have been developing palladium catalysed cyclization–anion capture cascades that result in the formation of one or more rings with concomitant introduction of a wide range of functionality by replacing the β-hydride elimination step of a Heck reaction with a group or atom transfer.1 This versatile and wide ranging methodology is summarized in Table 1and illustrated for a bis-cyclization sequence with an aryl starter species in Scheme 1.2

The starter species is usually

Cyclocarboformylation

The catalytic hydroformylation of alkenes is a major industrial process9 which has attracted a substantial number of applications in fine chemical synthesis.10.(a), 10.(b), 10.(c) A related process of similar wide potential would be catalytic carboformylation (Scheme 2). Cyclocarboformylation, in which RX and the alkene are contained within a single molecule, can potentially be accessed by a termolecular queuing process of which Scheme 3is a typical example.

Molecular queuing processes employing

Experimental

Melting points were determined on a Koffler hot-stage apparatus and are uncorrected. Infrared spectra were recorded on Perkin-Elmer Model 598 and 983G instruments and refer to films unless otherwise noted. Mass spectral data were obtained from a VG AutoSpec operating at 70 eV. Nuclear magnetic resonance spectra were recorded on Bruker QE 300 and AM 400 machines operating at 300 and 400 MHz, respectively. Unless otherwise specified, deuterochloroform was used as solvent with tetramethylsilane as

Acknowledgements

We thank Leeds University, AstraZeneca, Organon and the EPSRC for support.

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