are well-known compounds141, the thiooxoketones (9) and dithiones (10) are new compounds. Their structures have been determined by high resolution NMR and mass spectrometry; an X-ray structure of (9a) confirmed the assignments.The first step of the synthesis-the formation of the cyclic diureas (4) or (5)-is supported by the hydrolysis of (4) to (11) in quantitative yields. The second step-the unsymmetric transannular ring closure (see Scheme 1)-might well beaccelerated by the concurrent regeneration of the isocyanate or isothiocyanate group and release of the imidazole moie-tY.The above mentioned successive application of two reagents permits the synthesis of the unsymmetric product (9) in two ways: from (1) with (2) and (7) via (4) or with (3) and (6) via (5). Moreover, this approach replaces composite reagents (carbonyl i~ocyanates~~] or isothiocyanatesI6]) by simple ones 1(4, (3), (6), ( 7~.
ExperimentalA 0.5 M solution of (la) in benzene is gradually mixed at room temperature with a 0.5 M solution of (3) in benzene (using a Sage syringe pump; Orion, Research Inc.). The resulting crystalline precipitate is dissolved in DMF and treated with 1.5 equivalents of (6) and heated for 30 min under reflux. The reaction mixture is then allowed to cool to room temperature and the product hydrolyzed by addition of 10 ml of 5% isopropanol and heating for 15 min under reflux. Evaporation of the solvent yields a syrup-like oil from which the azepine (9a) is isolated by chromatography in 70% yield.-@) and (10) were prepared under analogous reaction conditions in comparable yields.
Die Umsetzung des leicht zugänglichen Spirokohlenwasserstoffs (II) mit Organolithium‐ bzw. ‐dilithiumverbindungen und anschließende Zugabe von Wasser führen zu den thermolabilen Verbindungen (I) bzw. (III) als Isomerengemischen, die durch NMR‐, IR‐ und MS‐Spektren charakterisiert wurden.
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