The activation and oxidation of alkenes using either osmium or palladium catalysis are compared. Osmium has been the metal of choice for dihydroxylation and aminohydroxylation of alkenes; however, palladium can now achieve comparable reactions and in some circumstances is more readily accepted than osmium.

F o r m a t i o n o f O x a z o l i d i n o n e s o r A l l y l i c A m i d e s f r o m a C o m m o n P r e c u r s o rAbstract: The use of palladium to effect two different reactions on a common starting material is presented. With a copper oxidant, an aminohalogenation is achieved to produce oxazolidinones. When the copper is absent, a [3,3]-sigmatropic rearrangement takes place to produce allylic amides.The progress of research into organometallic reagents in the last 40 years is perhaps epitomized by looking at the entries for 'palladium' in Synthesis since its inception in 1969. In the 1970s there are a few mentions of palladium -notable mostly as palladium(II) reactions. However, the frequency of articles using the transition metal increases in the 1980s and 1990s, and most dramatically in the late 1990s and 2000s, with a bias towards palladium(0)-mediated processes. There is obviously still an increasing use of transition-metal mediated reactions and, of these, palladium is among the most common. As such, we wish to present our results on two palladium-mediated reactions. Of particular note is the versatility of the catalyst to effect different reactions on the same substrate through judicious choice of reaction conditions. We were initially looking at a means through which to activate alkenes towards functionalisation with heteroatoms, principally oxygen and nitrogen. For the most part, dihydroxylation and aminohydroxylation reactions have been the domain of osmium, but we recently highlighted that there is a complementary role played by palladium in related reactions. 1 Most notable on this front is the recent work by Stahl 2 and Sorensen 3 who have shown that palladium can produce highly functionalised aminohydroxylation products from alkenes. We were keen to look at the use of tethered systems, which would provide a means to control regiochemistry and perhaps also stereochemistry. To this end, we started with systems such as those shown in Scheme 1. Here, we were concerned with the palladium(II)-mediated reaction of carbamates with pendant olefins to produce the corresponding heterocycles. This type of reaction has been achieved by Donohoe 4 with osmium in an aminohydroxylation reaction and, more recently, with palladium by Stahl 2 and Sorenson. 3 We have initially investigated aminohalogenation reactions of tethered systems. Lu 5 and Chemler 6 have reported on this type of reaction, however, both groups utilized tosyl protecting groups on the nitrogen. More recently, Michael has illustrated a related reaction employing a tridentate palladium catalyst. 7 We were keen to avoid the use of tosylate as it can present difficulties in removal, and we were also interested in the possibility of combining several reactions into one pot. We therefore chose the trichloroacetyl group, which appeared to fit the profile of providing the necessary protection and reactivity for the nitrogen, whilst also being relatively straightforward to remove by several different methods. We started by preparing the requisite carba...

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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.