Application of the Nicholas reaction to the synthesis of dicobalt hexacarbonyl complexed diyne ethers

Addition of propargylic or homopropargylic ynols to dicobalt hexacarbonyl propargylium cations gave the expected ether products of the Nicholas reaction, with the exception of 4-phenyl-3-butyn-1-ol which gave a dihydrofuran due to propargylium cation promoted 5-endo ring-closure. Use of chiral dicobalt hexacarbonyl complexed propargylic ynols as both propargylium cation precursor and nucleophile gave racemic doubly complexed disymmetric diyne ethers, each as a single diastereoisomer. Addition of dicobalt hexacarbonyl complexed 1-phenyl-1-butyne-3-ene to the propargylium cation derived from dicobalt hexacarbonyl complexed 1-phenyl-1-butyn-3-ol, followed by the addition of a nucleophile (NuH), gave double complexed 1,7-diphenyl-3-Nu-5-methylhepta-1,6-diynes (d.r. > 10:1).

Graphical abstractAddition of propargylic or homopropargylic ynols to dicobalt hexacarbonyl propargylium cations gave the expected ether products of the Nicholas reaction. Use of chiral dicobalt hexacarbonyl complexed propargylic ynols as both propargylium cation precursor and nucleophile gave racemic doubly complexed disymmetric diyne ethers, each as a single diastereoisomer.Figure optionsDownload full-size imageDownload as PowerPoint slide