
TY  - JOUR
A1  - Crumbie, RL 
A1  - Ridley, DD 
A1  - Steel, PJ 
T1  - Stereoselectivity in the Reactions between the Anion of 4-Phenyl-5,6-dihydro-2<i>H</i>-thiopyran 1-Oxide and Electrophiles
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1985
VL  - 38
IS  - 1
SP  - 119
EP  - 132
KW  - 
UR  - https://doi.org/10.1071/CH9850119 
N2  - 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. 
ER  -

