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Synthesis and Heck Reactions of Ethenyl‐ and ( Z )‐Butadien‐1‐yl Nonaflate Obtained by the Fragmentation of Furan Derivatives
Author(s) -
Lyapkalo Ilya M.,
Webel Matthias,
Reißig HansUlrich
Publication year - 2001
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200111)2001:22<4189::aid-ejoc4189>3.0.co;2-i
Subject(s) - chemistry , enol , silylation , medicinal chemistry , heck reaction , organic chemistry , aldehyde , cycloisomerization , crotonaldehyde , furan , palladium , catalysis
The nonaflation of lithium enolates or of silyl enol ethers, formally derived from acetaldehyde or crotonaldehyde, with nonafluorobutanesulfonyl fluoride gave ethenyl nonaflate ( 1b ) and ( Z )‐buta‐1,3‐dien‐1‐yl nonaflate ( 2 ) in good yields. The required enolates were obtained by aldehyde‐free routes by the lithiation of tetrahydrofuran or 2,5‐dihydrofuran followed by the cyclofragmentation of the metallated heterocycles. The application of this approach to the synthesis of allenyl nonaflate 3 failed, presumably due to the intrinsic instability of this allene derivative. The nonaflates 1b and 2 were also prepared by the fluoride‐catalysed reaction of the corresponding silyl enol ethers 5 and 7 with nonafluorobutanesulfonyl fluoride; however, the overall yields are slightly lower for these two‐step pathways. The cyclofragmentation of lithiated 2,2‐dimethyl‐4‐methylene‐[1,3]dioxolane allowed the easy preparation of trimethylsiloxyallene ( 10 ) in moderate yield. The nonaflates 1b and 2 reacted smoothly with monosubstituted alkenes in the presence of a catalytic amount of palladium(II) acetate to give the anticipated Heck coupling products in good to moderate yields and with high stereoselectivities.