Synthesis of spiro(2.4)hepta-1,4,6-triene

[摘要] A two-step synthesis of spiro(2.4) hepta-1,4,6-triene 1 is described. The starting material 2 was synthesized by irradiation of diazocyclopentadiene in the presence of (2-bromovinyl)trimethylsilane. The predominant formation of the trans isomer probably reflects the isomeric composition of the starting alkene (cis:trans ratio $approx$ 10:90). Elimination of 2 using CsF in dimethyl sulfoxide yielded 1.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE MAI) Spiro (2.4) hepta-1,4,6-triene is remarkably stable. $msp1H$ and $msp{13}C$ NMR data could be obtained at room temperature. The infrared spectrum exhibits a moderately strong absorption at 1713 $m cmsp{-1}$ characteristic of cyclopropenes. The ultraviolet spectrum of spiro (2.4) hepta-1,4,6-triene recorded in methanol has $lambdasb{m max}$ = 254 nm, very close to that reported (257 nm) for 3. This observation is in conflict with theoretical predictions which claim that 1 will experience a small hypsochromic shift resulting from spiroconjugation.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE MAI)

[发布机构] Rice University