Dienes hydrobromination

The reactions were cleaner than those with cis,cis-1,5-cyclooctadiene, and purification of the intermediate bis-mercurated peroxide was unnecessary. Indeed, it was a simple matter to isolate 52 (28 %) and 53 (38 %) from crude products obtained using a sample of 1,4-cyclooctadiene containing 30% of cis,cis-1,5-cyclooctadiene, which is readily accessible via hydrobromination-dehydrobromination of the 1,5-diene. Two of the diastereoisomers of 53 were separately isolated by HPLC and the most... 

Xfi-Dienes. The reagent undergoes a light-catalyzed regioselective addition to al-kenes, particularly mono-, 1,1-di-, and trisubstituted alkenes. The adducts undergo de-hydrobromination to a,p-unsaturated bromomethyl sulfones. On treatment with potassium... 

Addition of dibromocarbene to bicyclo[3.2.1]octa-2,6-diene, under the basic conditions used to generate the carbene, yielded 3,4-dibromobicyclo[3.3.l]nona-2,7-diene (27), which was de-hydrobrominated on treatment with potassium ter/-butoxide in dimethyl sulfoxide, to give 3-bromotricyclo[3.3.1.0 ]nona-3,6-diene (28). ... 

A novel way of studying a partially reacted polydiene is to deconnpose it in a metathesis reaction with a small olefin then to separate and identify the low molecular weight products by standard methods such as gas chromatography-mass spectrometry. This method has been applied to polybuta-1,4-diene partially aralkylated or hydrobrominated, to confirm the structure and position of the substituents. " The small olefin was oct-4-ene and the metathesis was promoted by a WCU/Sn(CH3)4 catalyst. The products of such a metathesis breakdown are, of course, dependent also on the nature and distribution of double bonds within the parent polymer. ... 

The extreme readiness with which tetrafluoroallene homopolymerises has prevented a study of the orientation of free-radical attack on the allenic system. Perfluoropenta-1,2-diene, however, does not polymerise readily, and so its photochemical chlorination and hydrobromination have been studied. ... 

Though inert towards chlorine at room temperature in the dark, perfluoropenta-1,2-diene is rapidly converted into the saturated tetrachloride, 1,2,2,3-tetrachloro-octafluom-n-pentane (95 %), and a small amount of mixed dimers, (CjFjIj (4%), when photolysed in the presence of an excess of chlorine. Photochemical hydrobromination yields mainly 3/f-2-bromo-octafluoropent-1-ene (34) and 1 W-2-bromo-octafluoropent-2-ene (35), a result which indicates that bromine atom preferentially attacks the central carbon of the allenic system to give an intermediate radical (36) which exists long enough to permit 90° rotation of the orbital containing the unpaired electron, so that it is transformed into an allylic radical (37) (see Scheme 14). 

---