
TY  - JOUR
A1  - Haynes, RK 
A1  - Vonwiller, SC 
A1  - Hambley, TW 
T1  - Stereoselection in the Aprotic Conjugate Addition Reactions of Lithiated 1-Isobutylbut-2-enyl Sulfoxide, Sulfone and Phosphine Oxide With Cyclopent-2-enone and Methylcyclopent-2-enone
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1989
VL  - 42
IS  - 10
SP  - 1671
EP  - 1684
KW  - 
UR  - https://doi.org/10.1071/CH9891671 
N2  - Lithiated 4-(t- butylsulfinyl)- and 4-(t-butylsulfonyl )-6-methylhept-2-ene, and [(E)-1-isobutylbut-2-enylldiphenylphosphine oxide, undergo conjugate addition with cyclopent-2-enone and 2-methylcyclopent-2-enone to deliver mixtures of diastereomers arising from reaction through C3 of the allyl system. The relative configuration of the major product obtained from the lithiated phosphine oxide and 2-methylcyclopent-2-enone has been determined by an X-ray crystallographic study. The proportions of diastereomers formed are rationalized in terms of carbanions which have a low barrier to rotation about the C1-C2 bond of the allyl system, and steric interactions prevailing in the trans-decalyl and related transition states experienced by the reactions. The reaction of the lithiated phosphine oxide with 2-methylcyclopent-2-enone has a diastereoselection useful for synthetic approaches towards vitamin D derivatives. 
ER  -

