Projects per year
Abstract
The effect of organolithium reagent (RLi: R = n-Bu, i-Pr, s-Bu, t-Bu), solvent (diethyl ether, diethyl ether/THF and MTBE), and stoichiometry on the (–)-sparteine-mediated silylation of 7,8-dipropyltetrathia[7]helicene shows that, unusually, substantially more than 0.5 eq of RLi (R = i-Pr, s-Bu, t-Bu) and a large excess of (–)-sparteine (R = n-Bu, s-Bu) is often needed to achieve substantial conversions and good e.e.s. With n-BuLi, however, just 1 equivalent of the organolithium reagent is sufficient. Our best results were obtained using the convenient t-BuLi/(–)-sparteine adduct with which the need for a high (–)-sparteine:RLi ratio can be avoided. Single- and double-KR procedures give enantiopure samples of 2-trimethylsilyl- and 2,13-di(trimethylsilyl)-7,8-dipropyltetrathia-[7]helicene and two-step double-KR combining (–)-sparteine/s-BuLi and chiral formamides affords the synthetically valuable 2-formyl-7,8-dipropyltetrathia[7]helicene. This is the first use of (–)-sparteine for the enantioselective lithiation of helicenes and the first report of t-BuLi outperforming s-BuLi in a (–)-sparteine-mediated procedure.
Original language | English |
---|---|
Pages (from-to) | 18677-18689 |
Number of pages | 13 |
Journal | Chemistry - A European Journal |
Volume | 21 |
Issue number | 51 |
Early online date | 12 Nov 2015 |
DOIs | |
Publication status | Published - 14 Dec 2015 |
Keywords
- Tetrathia[7]helicenes
- Asymmetric Synthesis
- (–)-Sparteine-mediated lithiation
- Kinetic Resolution
- Double-KR
Profiles
-
G.Richard Stephenson
- School of Chemistry, Pharmacy and Pharmacology - Emeritus Professor
- Chemistry of Materials and Catalysis - Member
Person: Honorary, Research Group Member
Projects
- 2 Finished
-
A-I CHEM CHANNEL (INTERREG)
Stephenson, G. R., Arnaux, V., Bew, S., Bulman Page, P., Cammidge, A., David, F., Franck, X., Harrowven, D., Homme, A., Mulot, I., Munoz-Herranz, M. P., Richards, C., Rouden, J., Yves, R., Chan, Y. & Fernandes, I.
European Regional Development Fund
2/11/11 → 30/06/15
Project: Research
Research output
- 9 Citations (Scopus)
- 1 Article
-
Novel asymmetric formylation of aromatic compounds: Enantioselective synthesis of formyl 7,8- dipropyltetrathia[7]helicenes
Doulcet, J. & Stephenson, G. R., 14 Sep 2015, In: Chemistry - A European Journal. 21, 38, p. 13431–13436 6 p.Research output: Contribution to journal › Article › peer-review
Open AccessFile20 Citations (Scopus)21 Downloads (Pure)