Cl-CD-N=C=O(N-chlorocarbonyl isocyanate) is prepared in 90 % yield by partial hydrolysis of the addition product of phosgene and cyanogen chloride. Many derivatives of the iminocarboxylic acid parent compound can be obtained from this highly reactive species. Both the acid chloride and the isocyanate group are amenable to reactions exhibiting overall selectivity, and this opens the way, inter alia, to a simple preparative synthesis of isocyanates from alcohols, phenols, thiols, and thiophenols. Combination of the two functional groups and their peculiar symmetry, which becomes evident, e.g. in the HCI adduct, facilitates ready cyclization of N-chlorocarbonyl isocyanate under very mild conditions.

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Herrn P r o f . D r . Otto B a y e r i n m e m o r i a m gewidmet ZUSAMMENFASSUNG: Homopolymerisate aus 2-, 3-und 4-Trifluormethylstyrol, 4-Perfluorisopropylstyrol, 3,5-Bis-trifluormethyIstyrol und ein 1 : 1 Copolymerisat aus 2,4und 2,5-Bis-trifluormethylstyrol wurden hergestellt und Brechungsindices, Abbe-Zahlen sowie Glasubergangstemperaturen der Polymerisate bestimmt. Von diesen Thermoplasten ist das Poly-2-trifluormethylstyrol im Hinblick auf optische Anwendungen besonders interessant, da es in einem weder von anorganischen Glasern noch von bekannten thermoplastischen Kunststoffen bisher erreichten Gebiet des n-v -Diagrammes liegt. Die wichtigsten mechanischen und thermischen Eigenschaften dieses Polymeren und die Copolymerisationsparameter fur die binare Copolymerisation von 2-Trifluormethylstyrol mit Styrol, Methylmethacrylat und n-Butylacrylat wurden bestimmt. Optische Daten und Glastemperaturen einiger Copolymerisate des 2-Trifluormethylstyrols werden mitgeteilt. SUMMARY: Homopolymers of 2-, 3and 4-trifluoromethylstyrene, 4-perfluoroisopropylstyrene, 3,5-bis-trifluoromethyl-styrene and a 1 : I copolymer of 2,4-and 2,5-bis-trifluoromethyl-styrene have been synthesized and t h e refractive indices n Abbe-numbers vD and glass transition temperatures of t h e polymers have been deylrmined.With regard to optical applications poly-2-trifluoromethyl-styrene is particularly interesting since its optical properties a r e in a region of t h e n-vdiagram t h a t has not been reached by thermoplastic polymers or inorganic glasses before.The most important mechanical and thermal properties of this polymer a r e reported Reactivity ratios of t h e binary copolymerisation of 2-trifluoromethyl-styrene with styrene, methyl-methacrylate and n-butyl-acrylate a r e listed as well as optical d a t a and glass transition temperatures of some copolymers of 2-trifluoromethyl-styrene.

(and ethylene) no other phototransformation of 14a takes place. With a half-life of ca. 12 min at 19°C the photoproduct 15a is thermally isomerized back to the diene diester 14a. Via a regiospecific addition of HCI, methanol and water to the tetracycles 15a and 15b (H2O) the epimeric products 18, 19 are isolated in a ratio of ca. 9: 1. Their structure is elucidated by oxidation of 18c to 21 and 'H-n.m.r. spectroscopic comparison with the isomeric compounds 20 and 22, resp., synthesized by a different route.Towards bishomodienophilic reagents like tetracyanoethylene and dimethyl acetylenedicarboxylate 15a shows the expected reactivity. The addition proceeds at the nonsubstituted edge of t h e bishomocyclobutadiene unit yielding 24 and 26.Bereits die ersten photochemischen Untersuchungen im Cyclohexa-1 ,CdienSystem 2 und den sich davon ableitenden 1,4-uberbruckten Homodienen 5 und 8 lieBen eine auffallende Divergenz im Reaktionsergebnis erkennen. In Derivaten des fast planaren Diens 2 konnte keine intramolekulare [2x + 2x1-Cycloaddition zu 1 erreicht werden; stattdessen lauft in der Regel eine Isomerisierung zu 3 ab2). Dem-

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