The magnesium-ene cyclization stereochemically directed by an allylic oxyanionic group and its application to a highly stereoselective synthesis of (+/-)-matatabiether. Allylmagnesium compounds by reductive magnesiation of allyl phenyl sulfides

The first example of a magnesium-ene cpclization stereochemically directed by an allplic oxyanionic group is demonstrated by a highly stereoselective synthesis of the bicyclic terpene matatabiether 10. The synthetic method is particularly valuable, not only because of the stereochemical control and the utility of the versatile hydroxyl group introduced into the product, ba t also because the precursor of the allylmagnesium is an allyl phenyl sulfi de, which is mon stable and more easily prepared in a connective fashion th an the usual allyl halide precursor. Since the presence of lithium ions enc ourages undesirable proton transfer to the cyclized organometallic and is d etrimental to the stereochemical control, the conversion of the allylic thi oether to the allylmagnesium utilizes a lithium-free method involving direc t reductive magnesiation in the presence of the magnesium-anthracene comple x.