Synthese, Photolyse und Thermolyse eines 1,4,4‐Trialkyl‐4,5‐dihydro‐5‐methylen‐1H‐1,2,3‐triazols. Hoch diastereoselektive Bildung des (E)‐2,2‐Dimethyl‐N‐neopentyl‐1‐cyclopropanimins

Abstract

Das 3,5-Dihydro-4H-l,2,3-triazol-4-on 13 reagiert glatt rnit Organolithiumverbindungen zu den tertiiren Alkoholen 14. Peterson-Olcfinierung oder -vicl bcsscr -Wittig-Olcfinicrung von 13 ergeben das erstc Dihydromethylen-l,2,3-triazol 17. Bcim Bestrahlcn ( h 2 320 nm) eliminiert 17 Stickstoff und bildet quantitativ und diastereoselektiv ( > 98% d.e.) das Cyclopropanimin (E)-22. Bei 70 C isomerisiert diescs rnit den Geschwindigkeitskonstanten k t L = 9.0. l O -' s -' und kll. = 15.0. . s-I).Obviously, the geometry of the H2C=k-N-CH2 group fixcd by the ring in 17 is retained to a large extent in the cyclopropanimine 22 formed, no matter whcther the molecular nitrogen is eliminated photochemically or thermally. The results are interpreted in terms of identical or very similar diradical intermediates on both routes, e.g. (E)-27, (E)-28, SdE)-30. In a way, these diradicals possess the partial structure of an (E)-1-azaallyl radical or a C = N double bond, respectively. which exhibits configurational stability. triazole 9 zu untersuchen. Wir berichten daher hier iiber die Synthese des ersten 5-Alkyliden-4,5-dihydro-l H-1,2,3-triazols 17, seine Thermolyse und das iiberraschende Ergebnis der photochemischen Stickstoff-Eliminierung.Synthese des 5-Methylen-4,5-dihydrolH-1,2,3-triazols 17 5-Alkylidendihydro-1,2,3-triazole 9 konnen prinzipiell als [3 + 21-Cycloaddukte von Allenen und Aziden 'OJ') oder von Keteniminen und Diazoverbindungen121 betrachtet werden. Umsetzungen dieser Verbindungen sind zwar wiederholt beschrieben worden, doch wurden dabei nie 5-Alkylidendihydro-l,2,3-triazole vom Typ 9 isoliert. So haben bereits 1968 Bleiholder und Shechter mit der gleichen Zielsetzung, die der vorliegenden Arbeit zugrunde Iiegt, elektronegativ substituierte Azide an Tetramethylallen addiert und die zum Teil (Ila-c) thermisch uberraschend stabilen, zu 9 isomeren Alkylidendihydro-1,2,3-triazole 11 erhalten. Deren photochemische (11 a) und thermische (11 d) Stickstoff-Eliminierung fuhrte jedoch nicht zu Alkylidenaziridinen 7 oder Cyclopropaniminen 8, sondern zu anderen Produkten (10 bzw. 12)")Chem.

Synthetic Molecular Motors: Thermal N Inversion and Directional Photoinduced CN Bond Rotation of Camphorquinone Imines

“…In addition to the expected pyrroline products 4,e thylene gas ( 1 HNMR signal at d = 5.41 ppm) was formed as well as isonitrile 5 (42 %; confirmed by X-ray crystallographic [a] 36:64 21:79 29:71 E/Z (PSS at 455 nm) [b] 99:1 99: structure determination), most likely by ap hotoinduced [2+ +2] cycloreversion reaction. [16,17] Most importantly,the two diastereomeric spirocyclic pyrroline products endo-4/exo-4 were obtained with an unbalanced d.r. value of 58:42, also indicating apreferred directionality in the C = Nbond rotation (see below).…”

Synthetic Molecular Motors: Thermal N Inversion and Directional Photoinduced CN Bond Rotation of Camphorquinone Imines

“…[16,17] Most importantly,the two diastereomeric spirocyclic pyrroline products endo-4/exo-4 were obtained with an unbalanced d.r. [16,17] Most importantly,the two diastereomeric spirocyclic pyrroline products endo-4/exo-4 were obtained with an unbalanced d.r.…”

“…structure determination), most likely by ap hotoinduced [2+ +2] cycloreversion reaction. [16,17] Most importantly,the two diastereomeric spirocyclic pyrroline products endo-4/exo-4 were obtained with an unbalanced d.r. value of 58:42, also indicating apreferred directionality in the C = Nbond rotation (see below).…”

Access to a Guanacastepene and Cortistatin-Related Skeleton via Ethynyl Lactone Ireland–Claisen Rearrangement and Transannular (4 + 3)-Cycloaddition of an Azatrimethylenemethane Diyl

“…These strained aziridines are converted into 2-amidoallyl cations 2 (Scheme ) upon acidic treatment that, in turn, may then be intercepted by suitably disposed dienes, exemplified by the formation of tetracycle 3 from MA 1 . Building from this work, we explored the possibility that azatrimethylene methane (ATMM) diyls might behave analogously . Feldman has shown that the thermal dipolar cycloaddition of azidoethyl allenes leads to loss of dinitrogen and formation of ATMM intermediates that, in the conjugated systems under study, immediately undergo ring closure, leading to cyclopenta­[ b ]­pyrrole derivatives ( 4 → 5 → 6 , Scheme ).…”