Ungesättigte Oxime, 22. Mitt. 2‐Alkoximino‐4‐phenylbutene

Abstract

4-Phenyl-3-buten-2-on-oxim(1) wird methyliert und benzyliert. Die isomeren Ether 3,4 und 5 lassen sich durch DC trennen und werden NMR-spektroskopisch untersucht. Unsaturated Oximes, XXII: 2 -A l k o~~-4 -p h e n y l b u t e n e s 4-Phenyl-3-buten-2-one oxime (1) is reacted with methylating and benzylating agents. The isomeric ethers 3.4 and 5 are separated by thin-layer chromatography and studied by nmr spectroscopy. Widerspruchliche Literaturangaben zu der Alkylierungsreaktion an Oximen waren Veranlassung fur uns, das Verhalten von (E)und (Z)-4-Phenyl-3-buten-2-on-oxim (1) zu untersuchen*). Wir setzten das bei der Darstellung anfallende (E/Z)-Gernisch 1 (E:Z-4:l) sowie die vorher d c getrennten Isomere (E) -1 und ( Z ) -1 und deren Natriumsalze zunachst mit einigen Methylierungsagentien um und uberpruften die 03h5-h?3317Y/~IY0Y~l7~~ s (12.SO/O

Photochemistry of the carbon–nitrogen double bond. Part 1. Carbon–nitrogen vs. carbon–carbon double bond isomerisation in the photochemistry of α,β-unsaturated oxime ethers: the benzylideneacetone oxime O-methyl ether system

“…structure (5). This is identical to that observed for isomers (2) and (3), providing support for the assignment of structures (4) and (5). product during the early stages of the reaction.…”

“…Compound (4) exhibits absorption maxima at 264 and 231 nm (E 13 750 and 8 350 respectively) whereas compound ( 5) absorbs maximally at 259 and 231 nm ( E 12 200 and 6 700 respectively). The extinction coefficients are smaller for the isomer assigned the Z,Z-structure (5). This trend is similar to that observed for the E,E-and Z,E-isomers (2) and that E-oximes derived from a,Punsaturated ketones and aldehydes (7) have higher R , values on t.1.c.…”

“…than the isomer assigned the 2-configuration, i.e. structure (5). This is identical to that observed for isomers (2) and (3), providing support for the assignment of structures (4) and (5).…”

“…Oxime 0-Methyl Ether (5).-(2)-Benzylideneacetone (6) was prepared '' by irradiation of (E)-benzylideneacetone (1) (7.0 g) in methanol (450 ml) at wavelengths > 300 nm for 2 h. The solvent was removed and the mixture applied to a flash chromatography column and eluted with light petroleum. (Z)-Benzylideneacetone (6) (3.3 g) [6 2.01 (s, 3 H, CMe), 6.5 (d, 1 H, J 12 Hz, vinylic H), 6.75 (d, 1 H, J 12 Hz, vinylic H), and 7.31 (m, 5 H, ArH)] eluted first, followed by (E)-benzylideneacetone (1) (3.2 g), and was used without further purification.…”