Photochemische [2+2]‐Cycloaddition zwischen parallelen CC‐ und NN‐Doppelbindungen

Abstract

Eine [π25s + π2s]‐Photocyclisierung zwischen nicht aktivierten CC‐ und NN‐Doppelbindungen wurde jetzt erstmals beim starren Molekül (1) beobachtet, das dabei in eine neuartige Käfigverbindung übergeht. In anderen Fällen scheiterte dieser Ringschluß an der rascheren N2‐Abspaltung.

Proximate,syn-Periplanar, Rigid Imine(Nitrone)/Ene-, and Diazene(Diazeneoxy)/Ene Systems: Syntheses, Homoconjugate Reactivity and Photochemistry

“…[42] In the dioxide 23, the olefinic protons (δ 14(15)-H ϭ 6.46) are deshielded relative to those of 17 (δ 14(15)-H ϭ 6.13); obviously the ONNO double bond exerts an anisotropic influence. In 28a(b) the rather tilted oxime C15ϭNO double bond is confirmed by the IR band at 1570 cm -1 and by the signal at δ ϭ 157.9 (157.1) in the 13 C NMR spectra. The oxadiazolidines 24 (25) and 37 are characterized i.a.…”

“…[15] ) amenable to competitive N 2 elimination. However, in an early paper by Hünig and Berning [13] it was demonstrated that even in a DBH-NϭN/CϭC system cycloaddition can win over N 2 elimination. [14] In the respective N-oxides, elimination of NO, N 2 O and N 2 O 2 is generally, if it occurs at all, only a very slow process.…”

“…Shift and multiplicity of the δ H ϭ 3.69 signal (17-H) suggested the transannular C-N bond between the ethano bridge and one of the nitrogen atoms (C17-N16). For the structural element ii bridging N11-N16-C21, the distinction of 9 13 C signals between δ ϭ 169 and 122 belonging to twofold substituted sp 2 -carbons and of two enamine/imine nitrogens (N-16, δ ϭ 87.1, N-11, δ ϭ 344.6) was decisive. Of these nine 13 C signals, six arose from CϭO groups of which one (δ ϭ 169) showed a coupling of J ϭ 7.0 Hz to a proton separated by 3 bonds.…”

“…For the structural element ii bridging N11-N16-C21, the distinction of 9 13 C signals between δ ϭ 169 and 122 belonging to twofold substituted sp 2 -carbons and of two enamine/imine nitrogens (N-16, δ ϭ 87.1, N-11, δ ϭ 344.6) was decisive. Of these nine 13 C signals, six arose from CϭO groups of which one (δ ϭ 169) showed a coupling of J ϭ 7.0 Hz to a proton separated by 3 bonds. Of the other 3 signals, the one at δ ϭ 151.3 is split by coupling to two protons (J ϭ 5.0, 9.0 Hz), while the remaining two (δ ϭ 142.8, 122.2) appear as singlets.…”

Iron Carbonyl Assisted Synthesis of 1,2-Diazepin-3-ones from Cyclic Diazenes and Alkynes

“…0340-5087/85/0200-0187/$ 01.00/0 plexation to undergo C-N bond formation with alkynes. In the organic chemistry of the N=N group, reactions with unsaturated hydrocarbons are known to occur only if the diazene group is activated by electron withdrawing groups in the a,a'-position, like the Diels-Alder reaction with dienes [8], or if favoured by a special steric situation like the intramolecular [2+2] photocycloaddition with a C=C bond [9].…”