ISSN:
0009-2940
Keywords:
Stannanes, α-(alkylthio)
;
Wittig rearrangement
;
Configurational stability
;
α-Lithio sulfides
;
[2,3] Rearrangement
;
Stereoselectivity
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The nBuLi-induced tin/lithium exchange reactions of the di-astereomeric γ-[(methoxyethoxy)methoxy]-]α-(tributylstannyl) sulfides anti- and syn-8 delivered the α-(lithioalkyl) benzyl sulfides anti- and syn-11, respectively. Within 1 h at -78°C, these species underwent [2,3]-thia-Wittig rearrangements in THF via the de-aromatized cyclohexadiene intermediates syn- and anti-12. Tautomerization and protonation yielded 81:19 (85%) and 19:81 mixtures (96%) of the ortho-functionalized toluenes syn- and anti-13. Probably, both Wittig rearrangements proceeded with 100% inversion of configuration at the carbanionic stereocenter, and the overall loss of stereoselectivity is due to an epimerization anti-11 ⇌ syn-11 of the lithio sulfide intermediates at a rate which is 3.3 times slower than the rearrangement.
Additional Material:
2 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19941271019
Permalink
