ISSN:
1434-193X
Keywords:
Aliphatic sulfine
;
Organolithium, thiophilic addition of
;
Carbanions
;
Protonation
;
Stereoselectivity
;
Sulfur
;
Lithium
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Protonation of α-sulfinyl carbanions 3, resulting from the selective thiophilic addition of organolithium compounds to aliphatic sulfines 2, provided dithioacetal oxides 4 (63-94% yield). The diastereomeric ratio ranged from 52:48 up to 100:0 with sterically hindered substituents. Thus, (1S*,SS*)-2,2-dimethyl-1-methylsulfanyl-1-methylsulfinylpropane (4ca) was obtained as a single isomer. The origin of the stereoselectivity is rationalized in terms of a thermodynamic equilibrium between the two diastereomers of α-sulfinyl carbanions 3, at which protonation occurs under kinetic control and with retention of configuration with the assistance of the lithium cation. Moreover, the stereochemistry could be totally reversed by converting the lithiated anion intermediate into an aluminium “ate” complex. Thus, (1R*,SS*)-2,2-dimethyl-1-methylsulfanyl-1-methylsulfinylpropane (4ca) was selectively obtained by this method (dr = 0:100).
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
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