ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The gas-phase structure of N,S,S-trimethylsulfoximine 1 and of its monolithiated isomers 2-4 was calculated by ab initio methods. It was found that a Li—C—S—N four-membered chelate 2 is the most stable isomer. The second minimum 4 shows N—Li—O complexation and is only slightly higher in energy. Li-Contacts with the C(α) atom and the sulfoximine O-atom in 3 are energetically disfavored by 6.1 kcal/mol. The two transition states 5 and 6 suggest an interconversion mechanism of 2 to 3 with 4 as an intermediate. A comparison of 4 with the crystal structure of the THF solvate 7, which was prepared by the addition of BuLi to (±)-S-(3,3-diphenylprop-2-enyl)-N-methyl-S-phenylsulfoximine (8) at low temperature in THF, demonstrates that the coordination geometry in the solid state is in good agreement with the calculated structure. The (1-lithioallyl)sulfoximine 7 crystallized as a centrosymmetric dimeric aggregate featuring an eight-membered ring with the atomic sequence (Li—N—S—O)2. The O-atoms of two THF molecules and the sulfoximine O- and N-atoms are coordinated to the Li-atom in a tetrahedral orientation. After metallation, a significant shortening of the S—C(α) bond is observed. Remarkably, only one of the two possible diastereoisomeric enantiomer pairs is found in the solid state.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19960790324
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