139913-95-4Relevant academic research and scientific papers
Highly cis-selective Wittig reactions employing α-heterosubstituted ylids
Zhang, Xin-Ping,Schlosser, Manfred
, p. 1925 - 1928 (1993)
1-Alkenyl chlorides, bromides or iodides can be obtained with very high cis selectivities through Wittig reaction employing α-chloro, α-bromo α-iodo ylids derive from tris(2-methoxymethoxyphenyl)phospine. The corresponding α-methoxy substituted ylid produces enethers with again remarkably high cis/trans ratios. Palladium(II) catalyzed coupling of (Z)-1-iodo-1-heptene with ethyl acrylate affords ethyl (2E,4Z)-2-4-decadienoate, the Bartlett pear fragrance, with almost quantitative yield.
Laser flash photolysis study of substituent effects on the rate of 1,2-H migration in a series of benzylchlorocarbenes
Liu, Michael T. H.,Bonneau, Roland
, p. 3604 - 3607 (2007/10/02)
Laser flash photolysis of para-substituted 3-chloro-3-benzyldiazirines in isooctane produces the corresponding carbenes, which react with pyridine to form ylides or undergo 1,2-H migration to form the (Z)- and (E)-β-chlorostyrenes. The rate for the 1,2-H migration is determined by plotting the pseudo-first-order rate constants for the growth of the ylide vs [pyridine] and extrapolating to zero pyridine concentration. In the case of (p-chlorobenzyl)chlorocarbene, the carbene decay can be monitored directly at 310 nm, whereas in [p-(trifluoromethyl)benzyl]chlorocarbene, the 285-nm trace may be analyzed as the sum of the absorption of the carbene and of the product β-chlorostyrenes. A Hammett plot of the logarithms of the rate constants for 1,2-H migration vs σp values gave a ρ value of -1.0, consistent with a hydride-like 1,2-H shift to the carbene center. The rate constants for the cyclopropanation of carbenes with tetramethylethylene (TME) were determined. In particular, the cyclopropanation of (p-chlorobenzyl)chlorocarbene with TME gave a negative activation energy of -4.7 kcal mol-1.
