Ring Opening of Cyclopropane at 10 K

✍ Scribed by Prof. Günther Maier; Stefan Senger

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 274 KB
• Volume: 33
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.199405581

✦ Synopsis

Toa solulionofthe phosphonatereagcnt Z(1.1 cquiv, 0.01-0.02ni)and [18]crown-6 ( 5 equiv) in T H F at -78 C under argon was added 1 .O equiv of KN(SiMe,), (0.5 M in toluene). After 30 min. the resulting solutionYurry was added by cannula 10 a precooled ( -78 o r -100 C ) solution of 1 (2.1 -3.0 equiv) in THF. The reaction miyture was ctirrcd for 1-4 h at -78 or -100 C and then quenched r i t h 1 M acetic acid in McOH followed b) pH 7 phosphate buffer. Extractive workup (ethyl acetate). drying (MgSO,). and concentration gave the crude condensation product which as pui-ified by flash chromatography on silica gel by using 2 % EtOAc in hexaiies. Selected ' H NMR data (400 MHr. CDCI,): ( E ) -3 : 6 = 6.57 (dd. J = 15.8. 4.4 Hz. 1 H. CH=CHC(O), major diastereomer). 6.37 (dd. J , = 5 Hz, J1 not measurable (overlapping signals). l H. CH=CHC(O), minoi-diastereomerj. 6.35 (dt. J = 6 . 2 , 1.9Hr. I H ) . 5.50(dd. J=15.7. 1.XHr. I H ) . 4 . 8 4 ( t d . J = 1 0 . 7 . 4 . 4 H r . 1 H). : [ Z ) -3 : 6 = 6.33 (dd. J = 6.2. 1.7 Hr. 1 H). 6.11 (dd. .I = 11 7. 7.3 Hz. 1 H), 5.22 (tm. .I = 8.1 H z 1 H), 5.16 (dd. J = 11. 2 Hr. 1 H. CH=CffC(O). minor diastereomer). 5.09 (dd. J = 11.X. 2 0 H/, 1 H. CH=C/fC(O). major diastereomer). 4 78 (td, J = 10.7,4.4 HL. 1 H). 4.73 4.68 (m.

H ) .