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Versuche zur Messung des Betrages der Zirkularpolarisation sollen durchgeffihrt werden. L6sungen der Verbindung in C2Ha(OH)2 sind optisch inaktiv. Introduction. Three-dimensional data were collected to sin 0/2=0.66 A -1 on a card-controlled Enraf-Nonius three-circle diffractometer with nickel-filtered Mo K~ radiation (2=0.7107 A) (cf, Matthews, Stenkamp & Colman, 1973). Of 3729 reflections measured, 1429 were considered to have significant intensity [I> 2a(I)]. The crystal measured approximately 0.1 mm in each direction and had an absorption coefficient/z(Mo Kc 0 =25.3 cm -I. Systematic absences determined from Weissenberg and Buerger precession photographs were hOl for l odd, and 0k0 for k odd. A Patterson map provided starting coordinates for the bromine atom, and a Fourier synthesis, calculated with heavy-atom phases, clearly showed the remainder of the non-hydrogen atoms.Refinement by block-diagonal least-squares calculations, with isotropic temperature factors, resulted in an R value of 0.24. Anisotropic temperature factors improved R to 0.145 for the reflections with I>2a(I). The maximum and average final shifts were 0.0014 and 0-0008 A respectively for the bromine, and 0-019 and 0.005 A respectively for the remaining non-hydrogen atoms. A difference map, using low-angle data (sin/9/2 <0.32 A-l), did not clearly show all the hydrogen positions, and had positive and negative features up to 1 e A -3 in the vicinity of the bromine atom, presumably

Aus den beiden Acetylen‐zimtsäureamiden (Ia) und (Ib) entstehen beim Erhitzen in Gegenwart von Acetanhydrid die Cyclisierungsprodukte (II) und (III) bzw. (IV).

Beim Versuch der sauren Desacetylierung der Pyrrolinyl‐stilbene (Ia) und (Ib) erfolgt ein Ringschluß unter Umlagerung zu Benzo‐indolinonen (II), die erneut zu (III) acetyliert werden.