Living indene

When the ring system containing the sulfone moiety is unsaturated, a quite different set of products has been observed on photolysis, apparently arising from an initial cycloreversion to a short-lived sulfene intermediate. For example, irradiation of 2H-1-benzothiopyran 1,1-dioxide (41) in dichloromethane or methanol gave the cis- and trans-sultines (42) and the ring-expanded sultine (43) in roughly equal amounts, accompanied by minor amounts ( 5%) of the products of formal loss of S02, i.e. indene, and SO, i.e. 4472... 

As mentioned above, persistent carbocation 9 underwent rearrangement into cation 10 which rearranged further into cation 11. To reveal general relations/factors governing cationic rearrangements in benzopentalene derivatives, the behavior of 5,5,10,10-tetramethyl-5,10-dihydroindeno[2,l-fl]indene (12) in superacids was studied (52). It had been expected that hydrocarbon 12 would transform into the long-lived 5,5,10,10-tetramethyl-4b,5,9b,10-tetrahydroindeno[2,l-a]inden-4b-yl cation (13). However, H and 13C NMR data showed that hydrocarbon 12 transformed firstly into isomeric ion 14 which transformed further into cation 15 (Scheme 11). 

Monitoring data on 2,3-benzofuran in environmental media are scarce. Potential human exposure to 2,3-benzofuran may occur by ingestion of foods treated with coumarone-indene resin however, migration of 2,3-benzofuran from this resin has not been confirmed. Occupational exposure to 2,3-benzofuran may occur in several energy-related industries, and individuals living in the vicinity of hazardous waste sites at which this compound has been detected may also be exposed. The EPA has identified 1,177 NPL sites. 2,3-Benzofuran has been found at 5 of the sites evaluated for the presence of this chemical (View 1989). However, it is not known how many of the 1,177 NPL sites have been evaluated for 2,3-benzofuran. As more sites are evaluated by the EPA, the number may change. The frequency of the sites in the United States at which... 

One of the issues that concern liquid feedstock cracking operations is a higher rate of fouling. This is not only a consequence of heavier coke forming precursors, but also as a consequence of long lived free radicals which act as agents for the formation of a polymer (often referred to as pop-corn polymer) in the primary fractionator and downstream units. For instance, free radicals based on styrene or indene have sufficiently long half-lives to pass from the pyrolysis section into the primary fractionator. These can concentrate in this unit and produce polymer (free radical polymerisation) when sufficient amounts of suitable olefins are present, in particular styrene itself and di-olefins such as cyclo-pentadiene or butadiene. 

The heterocyclic 5,5-difluoro-l//-thiacyclopropa / indene (12) was synthesized by eycloaddi-tion of the appropriate cxocyclic diene to l,2-dichloro-3,3-difluorocyclopropene, in analogy to the synthesis of the parent hydrocarbon/°° but was too short-lived to allow full characterization/ The oxa analog, in turn, could not be isolated. No difficulties were encountered with the 1,3-dihydro derivatives of 5,5-difluoro-5//-cyclopropa[/][2]benzothiophene 10a and 10b. "... 

It is also possible to carry out living cationic polymerization of isobutylene, initiated by a difiinctional initiator." This results in a formation of bifunctional living segments of polyis-obutylene that are soft and rubbery. Upon completion of the polymerization, another monomer, one that yields stiff segments and has a high Tg value, like indene, is introduced into the living charge. Polymerization of the second monomer is initiated from both ends of the formed polyisobutylene. When the reaction is complete, the polymerization is quenched. Preparations of a variety of such triblock and star block polymers have been described." ... 

Kennedy [16] has described the formation of a triblock polymer with a center block based on IB and end blocks based on indene. By using an initiator that is difunctional, the center block has two living ends so that both end blocks are added simultaneously. In one example shown in Figure 4.9, IB can be initiated from a... 

FIGURE 4.9 (a) Synthesis of a triblock copolymer of IB and indene (In) by cationic polymerization. (Data from Kennedy, J. R, and B. Ivan, Designed Polymers by Carbocationic Macromolecular Engineering, Hanser Publishers, New York, 1992.) (b) Synthesis of polyvinyl ether using living cationic initiator. (Data from Teyntjens, W. G. S., and E. J. Goethals, Polym. Adv. TechnoL, 12,107, 2001.)... 

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