Access to benzo-fused nine-membered heterocyclic alkenes with a trifluoromethyl carbinol moiety via a double decarboxylative formal ring-expansion process under palladium catalysis.

Pulakesh Das,Hiroto Uno,Punna Nagender,Etsuko Tokunaga,Satoshi Gondo,Norio Shibata

doi:10.1039/c7sc05447e

Pulakesh Das, Hiroto Uno + Show 4 more

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https://doi.org/10.1039/c7sc05447e

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Abstract

Direct access to pharmaceutically attractive benzo-fused nine-membered heterocyclic alkenes 3 with a trifluoromethyl carbinol moiety was achieved via a palladium-catalyzed double-decarboxylative formal ring-expansion process from six-membered trifluoromethyl benzo[d][1,3]oxazinones 1 to nine-membered trifluoromethyl benzo[c][1,5]oxazonines 3 in the presence of vinylethylene carbonates 2. Generation of a Pd-π-allyl zwitterionic intermediate was proposed in the catalytic cycle. The trifluoromethyl group in the benzoxazinanones 1 plays an important role throughout the transformation. Diastereoselective chemical transformations of products 3 were also demonstrated.

Highlights

Fluoro-functionalized heterocycles with diverse ring sizes and ring systems have been well studied in pharmaceuticals and agrochemicals.[1]
We started a preliminary investigation with the reaction of tri uoromethyl (CF3) benzoxazinanone 1a and phenyl vinylethylene carbonate 2a in the presence of suitable palladium precursors and/or phosphine ligands (Table 1)
A combination of tri uoromethylated six-membered benzoxazinanones with vinylethylene carbonates resulted in direct access to previously unknown tri uoromethylfunctionalized nine-membered heterocycles

Summary

Introduction

Fluoro-functionalized heterocycles with diverse ring sizes and ring systems have been well studied in pharmaceuticals and agrochemicals.[1]. Scheme 1 Direct access to benzo-fused nine-membered heterocyclic alkenes 3 with a trifluoromethyl carbinol moiety from sixmembered oxazinones 1 and vinylethylene carbonates 2 via palladium-catalyzed double decarboxylative cycloaddition and the further diastereoselective chemical transformations of 3. We started a preliminary investigation with the reaction of tri uoromethyl (CF3) benzoxazinanone 1a and phenyl vinylethylene carbonate 2a in the presence of suitable palladium precursors and/or phosphine ligands (Table 1).

Results

Conclusion