18913-35-4Relevant articles and documents
Retro-Ene Reactions in Acylallene Derivatives
Bibas, Herve,Koch, Rainer,Wentrup, Curt
, p. 2619 - 2626 (2007/10/03)
Allenic esters and amides 4 undergo a retro-ene reaction to vinylketene (6) and an aldehyde or imine (5) under the conditions of flash vacuum thermolysis (FVT). The same products are obtained by FVT of cyclobutenones 7 via electrocyclic ring opening to alkoxy- or aminovinylketenes 3 and 1,3-rearrangement of ketenes 3 to allenes 4. All the intermediates and products were characterized by matrix isolation IR spectroscopy, and in the case of 4c the reaction was also monitored by online mass spectrometry. A lower temperature for the retro-ene reaction of 4c, eliminating an imine, than for 4a, eliminating formaldehyde, is in agreement with a lower calculated activation barrier (167 and 181 kJ mol-1, respectively, at the G2(MP2,SVP) level of theory). The allenic amide 11 undergoes an analogous retro-ene reaction to the (unobserved) vinylketene 13, the latter isomerizing to cyclohexenylacrolein 16 in a 1,5-H shift (calculated barrier 125 kJ mol-1; G2 (MP2, SVP)).
METHANOLYSIS OF VICINALLY SUBSTITUTED TETRAHALOGENOBUTENES
Mavrov, M. V.
, p. 626 - 632 (2007/10/02)
The methanolysis of Z,E-1,2,3,4-tetrabromo-1-butene in the presence of strong bases leads predominantly to the formation of the ortho ester 1,1,1-trimethoxy-2,3-butadiene and the ether-acetal 1,1,4-trimethoxy-2-butyne.In the case of E-2,3-dibromo-1,4-dichloro-2-butene it leads predominantly to the ortho ester.During the reaction 10-12 linear unsaturated products containing 1-3 methoxyl groups are formed as side products.