
%0 Journal Article
%A Crumbie, RL 
%A Ridley, DD 
%A Steel, PJ 
%T Stereoselectivity in the Reactions between the Anion of 4-Phenyl-5,6-dihydro-2<i>H</i>-thiopyran 1-Oxide and Electrophiles
%J Australian Journal of Chemistry
%D 1985/01/01
%V 38
%N 1
%P 119-132
%K 
%R https://doi.org/10.1071/CH9850119
%U https://www.publish.csiro.au/paper/CH9850119 
%X Treatment of the anion(17), prepared from the six- membered ring allylic  sulfoxide 4-phenyl-5,6-dihydro-2H-thiopyran 1-oxide (8) with primary alkyl halides at -78&#176;, affords trans-2-alkyl-4-phenyl-5,6-dihydro-2H-thiopyran 1-oxides exclusively. The stereospecificity of these reactions thus corresponds to that obtained from the related saturated cyclic sulfoxides . However, when the anion (17) is treated with 2-iodopropane (-78&#176; &#8594; 20&#176;) a mixture of 2-cis and 2-trans products results. Independent experiments indicate that the lack of stereoselectivity is due to anion exchange reactions at the higher temperature required to effect alkylation. 2-cis and 2-trans Adducts also are obtained in reactions of the anion (17) with benzaldehydes (-78&#176; &#8594; 0&#176;), and from X-ray crystallographic analyses it has been established that the cis adducts predominate, with little selectivity in attack on the two enantiotopic faces of the aldehyde. 
