Stabilized cis-Tris-σ-homobenzenes: Syntheses, [σ2 + σ2 + σ2] Cycloreversions

✍ Scribed by Dipl.-Chem. Wolf Dieter Braschwitz; Dipl.-Chem. Thomas Otten; Dr. Christoph Rücker; Prof. Dr. Hans Fritz; Prof. Dr. Horst Prinzbach

• Publisher: John Wiley and Sons
• Year: 1989
• Tongue: English
• Weight: 354 KB
• Volume: 28
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.198913481

✦ Synopsis

rated without material loss by flash chromatography. The bismesylates 19 b/20 b, prepared under standard conditions in 85-90% yield, can be converted into the tetracyclic aziridine 21 b (70-85%) under the conditions used for 5 b (1 0 mmol, triphenylphosphane/THF). Cyclization of 21 b to 22 proceeds under the optimized conditions found for 1

( 5 mmol, 1.05 equiv. nBuLi/THF, -78 + + 20 "C) without any competition by the base-induced reactions typical of bicyclob~tanecarbonitriles~' 51 and azabicyclobutanes. Trituration of the crude product with ether affords a practicaliy quantitative yield of crystalline 22 (Z-3-azapentacyclo-[5.1.0.02~4.03~5.06~8]octane-7-carbonitrile), which remains unchanged up to its melting point (128 "C). The NMR data (Fig. 1) are characteristic for cyanocyclobutane and azabicyclobutane moieties. 23 2 4 H H 25 C H * -C ~H ~ 26 Saponification of 23, obtained by treatment of 22 with acetic anhydride, leads "directly" to oxaazapentacycle 24: reaction of 22 with Na,S (CH,Cl,/tBuOH, reflux) and with benzylamine/BF, (CH,Cl,/tBuOH, 50 "C) gives heterocycles 25 and 26, respectively (55-60%, not optimized).