Acylation of acetylenes. I. Observation of an intramolecular 1,5-hydride shift in a vinyl cation intermediate

Vinyl Carbocations Generated under Basic Conditions and Their Intramolecular C–H Insertion Reactions

“…The cycloheptene derivative 29 is a result of C–H insertion into cyclohexane from the ring-contracted exocyclic vinyl cation 31 . Finally, to further validate our C–H insertion step, we looked to disprove the possibility of 1,5-hydride migration, , given the selectivity in generating five-membered rings throughout our scope studies. Exposing tert -butyl derivative 32 to our reaction conditions yielded cyclohexene product isomers 33 in 85% NMR yield and a 1:1 ratio (Figure e).…”

Strong Bases and Weak Anions in Catalytic C–H Insertion Reactions of Vinyl Carbocations

“…The cycloheptene derivative 30 is a result of C-H insertion into cyclohexane from the ring-contracted exocyclic vinyl cation 32. Finally, to further validate our C-H insertion step, we looked to disprove the possibility of a 1,5-hydride migration [34][35] given our selectivity in generating five-membered rings throughout our scope studies. Exposing tert-butyl derivative 33 to our reaction conditions yielded cyclohexene product isomers (34)(35) in 85% yield and a 1:1 ratio (Fig.…”

Diastereoselective Synthesis of 2-Arylmethylene-6-hydroxyspiro[4.5]deca-7-ones via FeCl3·6H2O-Catalyzed Spiroannulation/Hydride Transfer of 6-(5-Arylpent-4-yn-1-yl)-7-oxabicyclo[4.1.0]heptan-2-ols

“…The residue was purified by flash chromatography over silica gel (3 × 13 cm, 10% ethyl acetate/ hexanes), providing (1S*,2S*,6R*)-6-(5-phenylpent-4-ynyl)-7-oxabicyclo[4. 9, 132.2, 128.6, 128.6, 128.1, 123.6, 89.0, 81.3, 66.9, 64.0, 61.3, 36.6, 29.1, 26.8, 24.0, 21.2, 19.4, 18.2; IR (CH 2 Cl 2 ) 3421,2940,2864,1715,1600,1448,784,692 6, 131.4, 128.9, 120.7, 88.5, 81.2, 66.8, 63.6, 61.2, 36.5, 29.1, 26.8, 24.0, 21.4, 19.4, 18. 6,131.4,128.9,120.7,88.5,81.2,66.4 (t,J CD = 21.7 Hz,1C),63.9,61.2,36.5,29.0,26.7,24.0,21.4,19.4,18. (1S*,2S*,6R*)-6-(5-(3,4-Dimethylphenyl)pent-4-yn-1-yl)-7-oxabicyclo[4.1.0]heptan-2-ol (1d). (0.600 g, 2.12 mmol, 75% from 0.750 g, 2.82 mmol of 3-(5-(3,4-dimethylphenyl)pent-4-yn-1-yl)-cyclohex-2-enone).…”