144563-67-7Relevant academic research and scientific papers
Tungsten η1-five-membered oxygenated heterocycles derived from tungsten η1-propargyl compounds: Systematic syntheses, structural rearrangement, electrophilic alkylations, and oxidative demetalations
Shu, Hsin-Guo,Shiu, Lin-Hung,Wang, Shin-Hwan,Wang, Sue-Lein,Lee, Gene-Hsian,Peng, Shie-Ming,Liu, Rai-Shung
, p. 530 - 540 (2007/10/03)
In the presence of BF3?Et2O, tungsten η1-propargyl complexes reacted smoothly with aldehydes to give tungsten η1-2,5-dihydro-3-furyl complexes 1-3. Treatment of 1-3 with Ph3CBF4 in CH2Cl2 (-60°C, 1 h) delivered tungsten η1-3-furylidene complexes 4-6 which underwent skeletal rearrangement to η1-furylidene 13-15 isomers when warmed to 5°C. Treatment of 4-6 with Et3N at -60°C produced tungsten η1-3-furyl complexes 7-9 which were isomerized to η1-2-furyl isomers 10-12 by a strong Bronsted acid. Protonation of 10-12 by CF3CO2H yielded η1-2-furylidene complexes 13-15. The two exceptional isomerizations were examined by in situ 1H NMR studies. Further oxidation of η1-2-furyl compounds 10-12 with m-chloroperbenzoic acid gave tungsten η1-Δ3-butenolides 16-18. Tungsten η1-3-furyl complexes 7 and 9 underwent alkylation with trimethoxymethane and aldehydes at -60°C to yield η1-3-furylidene cationic precipitates that were subsequently reduced with NaBH3CN to yield complex η1-2,5-dihydro-3-furyl compounds in good diastereoselectivity; the stereochemical courses were distinct for 7 and 9. Tungsten η1-2,5-dihydro-3-furyl, η1-2-furyl, η1-3-furyl, and η1-Δ3-butenolide complexes were decomplexed with appropriate reagents to liberate 2,5-dihydrofurans, furans, and Δ3- and Δ2-butenolides in reasonable yields.
