A NEW TIED-BACK APPROACH TOWARD THE SYNTHESIS OF TETRA-TERT-BUTYLETHYLENE

The extremely hindered selenadiazoline azoline-5',9''-3'',7''-dithiabi cyclo[3.3.1]nonane] (6) has been prepared as a precursor to ,5-dimethy l-3,7-dithiabicyclo[3.3.1]non-9-ylidene) (8), a 'tied-back'' analogue of tetra-tert-butylethylene (1). The pyrolysis of 6 yields retrocycliz ation and decomposition products and no 8, presumably due to strain li mitations. The ketone 1,5-dimethyl-3,7-dithiabicyclo[3.3.1]nonan-9-one (4) is unreactive toward McMurry coupling to 8.