The irradiation of 2,3-bis(tert-butylsulfonyl)norbomadiene (5) and 2-(tert-butylsulfony1)norbomadiene (6) yielded the expected quadricyclane derivatives as stable molecules. The Irradiation of 2,3-bi·;(tenbutyIsulfonyl)bicyclo[2.2.2]octa-2,5-diene (7), 2, .2]-octa-2,5-diene (8) and 8,9-bis(tert-butylsulfony1)-4-anti-phenyl-3,5-dioxa-exo-tricycJo(5.2.2.0 2 ,6] undeca-8, IO-diene 9a and its syn-isomer 9b yielded the corresponding tetracyclic and pentacycHc systems, respectively. The photoproducts of 8 and 9 reverted to the starting products slowly at room temperature, The halflife of the photoproduct of 7 was determined to be 34 min at 50·C, Compound 9a reacted with n-BuLi to yield the unexpected desulfonylation product 27a.The photochemistry of norbornadiene and many substitution products has been investigated in great detail, in and the methylene chain bridging the 2,3-positions of 2. This is supported by X-ray investigations on single crystals of 2. 3• However, if one tert-butyl-sulfonyl group in 2 was replaced by H, D, or CH 3 we found again prismane formaLion when the sample was irradiated." This difference in the behavior as a function of the substitution pattern made us look more closely at the photochemistry of the next higher sulfonyl substituted homologues of Dewarbenzenes, i.e. 2, -diene (9a) and its syn-isomer 9b.~S

The reaction of the AlC13 complex of cyclic diynes (mainly a 14-membered ring) with dimethyl acetylenedicarboxylate (DMAD) or bis(tert-butylsulfony1)acetylene (BTSA) and related compounds was investigated. The reaction of the A1C13 complex of cyclotetradeca-1,8-diyne (1, n = 5 ) with DMAD affords in 60% yield two isomers in a ratio of 7:3. The isomers were identified as the 1,4-and 2,3-bridged Dewar benzene derivative A and the 1,2-and 3,4-bridged Dewar benzene derivative B. Acetylenes with sterically more demanding groups such as BTSA or bis(diphenylphosphany1)acetylene P,P'-dioxide (BDPA) yield only the isomer A. The X-ray structures of the cycloadduct between 1 (n = 5 and 6) and BTSA, as well as of 2,3-bis(tert-butylsuIfonyl)-1,4,5,6-tetramethylbicyclo[2.2.0]hexa-2,5-diene (31) are described. The mechanism of the cycloadditions is discussed.

No abstract

In this paper we report on the photochemistry of Dewar benzenes bridged at the 1,4‐ and 5,6‐positions and substituted at the 2,3‐positions. It was found that simple alkyl substitution leads to prismanes only to a minor extent. Introduction of phenyl groups into the 2‐ or 2,3‐positions gives the corresponding doubly bridged prismanes in yields up to 80% Pentamethylene‐bridged bis‐Dewar benzenes 19 rearrange upon irradiation to 22. Irradiation of the doubly bridged Dewar benzene derivatives with one ester group at the 5‐position does not yield isolable products. However, introduction of one tert‐butylsulfonyl group such as 30–33 gives almost quantitative yields of isolable prismanes if pentamethylene or hexamethylene bridges are used. The nonbridged species, 2‐tert‐butylsulfonyl‐1,4,5,6‐tetramethylbicyclo[2.2.0]hexa‐2,5‐diene (44), aromatizes upon irradiation into 1‐(tert‐butylsulfonyl)‐2,3,4,5‐tetramethylbenzene (45). In contrast to the pentamethylene‐bridged monosulfone 47, the corresponding disulfone 38 undergoes no photochemical reaction. This could be explained by the X‐ray structure, which reveals a strong interaction between one of the tert‐butyl groups and the pentamethylene chain bridging the double bond in 38.

Reaction of a twofold excess of n-butyllithium with 1,6-bis(tert-butylsulfonyl)tetracyclo[4.2.0.05,7]octane (14) yields a mixture of 3- and 5-n-butyl-2-(tert-butylsulfonyl)bicyclo[2.2.2]octa-2,5-dienes 15 and 16, respectively, while the reaction with 2,3-bis(tert-butylsulfonyl)quadricyclane (11) leads to 5-n-butyl-2-(tert-butylsulfonyl)bicyclo[2.2.1]hepta-2,6-diene (24), and the reaction with 2-(tert-butylsulfonyl)hexacyclo[9.5.0.01,3.02,10.03,9.09,11]hexadecane (8) yields a 1:1 mixture of 15-n-butyltetracyclo[7.5.2.0.02,8]hexadeca-2(8),15-diene (34) and 1-n-butyl-2,3:4,5-dipentanobenzene (35). Common to all three reactions is the elimination of tert-butylsulfinate and the addition of a butyllithium moiety. A radical mechanism is suggested rather than an elimination via a strained double bond incorporated in a strained cage system.