Photochemische Stickstoff‐Eliminierung aus 3,5,5‐Trialkyl‐3,5‐dihydro‐4H‐1,2,3‐triazol‐4‐onen. Aziridinone, Iminooxirane und Folgeprodukte

Abstract

Bcim Bclichtcn (h > 300 nm) spalten Dihydro-1,2,3-triazolone 6Stickstoff ab und bilden in inerten Losungsmitteln bei -90 bis +20 C Aziridinone 7, 1: I-Gemische der Ketone 10 und Isocy- Die Photoextrusion von molekularem Stickstoff aus Stickstoflheterocyclen mit einer N = N-Gruppe als Ringglied, also cyclischen Azoverbindungen im weitesten Sinne, fiihrte zu einer breiten Skala interessanter Molekiile, die von sehr instabilen Diradikalen bis zu vollig bestandigen Verbindungen reicht ' ).Wohlbekannte Vorteile dieser photochemischen Methode gegeniiber anderen machen sie besonders attraktiv fur sehr energiereiche, weniger stabile Molekiile, die man sonst nur sehr schwer oder gar nicht erhalt. Wir haben daher auf diesem Weg aus Dihydroazolen 1 mit einer exocyclischen Doppelbindung, namlich 3,SDihydro-4H-pyrazolen 1, X' = X2 = CMe?) und 1,CDihydro-SHtetrazolen 1, X' = X2 = NR4-6), Heteromethylencyclopropane 2 synthetisiert. In einigen Fallen wurden ihre acyclischen Isomeren. die ..non-Kekul6"-Molekiile 3'). ESR-spektroskopisch nachgewiesen 'I, oder man erhielt andere Folgeprodukte dieser Diradikale@. Im Rahmen dieser Untersuchungen berichten wir hier iiber die Photolyse der Dihydro-l,2,3-triazolone 6').Ungesiittigte Substituenten wie VinyL6") oder Phenylgrupan den Dihydroazolen 1 ermoglichen die Cyclisierung von Zwischenstufen der Stickstoff-Extrusion zu fiinfgliedrigen Heterocyclen und beeinflussen damit entscheidend das Ergebnis. Wir beschrankten uns daher zunachst ;iuT Dihydro-I .2.3-triazolone 6 mit gesattigten AlkylsubstiPhotochemical Elimination of Molecular Nitrogen from 3.5,S-Trialkyl-3,-Wihydro-4H-I ,2.3-triazol4ones. Aziridinones, lminooxiranes and Products')The dihydro-l,2,3-triazolones 6 lose molecular nitrogen on irradiation (h > 300 nm).

Synthesis of Unsymmetrical Diolate, Oxametallacyclopentene, Amido-Alkoxide and Thiolato-Alkoxide Complexes Using Dialkyl and Diaryl Titanium Aminotroponiminate Complexes: A Route to Unsymmetrical Vicinal Diols

“…The major product of this reaction has been identified as the imine 2,6-Me 2 C 6 H 3 NCMe 2 , whereas with t -BuNC, t -BuNCMe 2 was formed. The assignment of imine products was confirmed by independent synthesis. ,

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“…CO gas (Airco) was used directly from the tank. TiR 2 L 2 , where L = Me 2 ATI, thiobenzophenone, and the imines N -tosylbenzaldimine, t -BuNCMe 2 , , and 2,6-Me 2 C 6 H 3 NCMe 2 were prepared by following literature procedures. Experiments were either performed in a nitrogen-filled glovebox or by conventional Schlenk line techniques under argon.…”

Mechanism of [2 + 1] Cycloadditions of Hydrogen Isocyanide to Alkynes: Molecular Orbital and Density Functional Theory Study

“…The mechanism and, in particular, the stereospecificity of these addition reactions have been investigated in details. − Owing to the presence of a monocoordinated carbon atom having an electron lone pair, isocyanides are also well suited as 1,1-dipolar partners in different types of cycloaddition whose primary cycloadducts undergo further rearrangements and/or ring expansions . Isocyanides have been known to add to doubly bonded dipolarophiles such as disilenes (R 2 SiSiR 2 ), diphosphenes (RPPR), , and silenes (R 2 CSiR 2 ). , Similar reactivities of isocyanides toward alkenes (R 2 CCR 2 ), ketones (R 2 CO), thioketones (R 2 CS), or analogous compounds are not reported yet, but the [2 + 1] cycloreversion of cyclopropanimines and other analogues of methylene-cyclopropanes, giving each an isocyanide plus a doubly bonded compound, have been well established. − In contrast, relatively little is known about the addition of isocyanides to alkynes. As far as we are aware, there are actually two reports by Krebs and co-workers , on the addition of aryl isocyanides to electron-rich or strained cyclic alkynes (eq 1) in which cyclopropenimines ( I ) could be isolated or trapped.…”

Time-Resolved IR Detection and Study of an Iminooxirane Intermediate

“…An iminooxirane intermediate was proposed to explain the products of the Lewis acid-catalyzed reaction of a carbonyl compound with an isocyanide . In addition, iminooxirane-derived products were also observed in both the thermal and photochemical decomposition of 3,5,5-trialkyl-3,5-dihydro-4 H -1,2,3-triazol-4-ones. , Quast and co-workers have also reported a comprehensive experimental and computational study of the thermal reorganization and cycloaddition reactions of a stable nonracemic chiral α-lactam, in which they observe iminooxirane-derived products . Using ab initio quantum mechanical calculations of the C 2 H 3 NO potential energy surface, they find that the parent α-lactam is approximately 7 kcal/mol lower in energy than the isomeric iminoxirane.…”