Cyclization by Intramolecular Carbolithiation of Alkyl- and Vinyllithiums Prepared by Reductive Lithiation: Surprising Stereochemistry in the Lithium Oxyanion Accelerated Cyclization
作者:Kai Deng、Ahlem Bensari、Theodore Cohen
DOI:10.1021/ja027988c
日期:2002.10.1
yield cyclopentylmethyllithiums by unconjugated organolithiums is greatly increased (1) by generating the organolithiums by reductive lithiation of phenyl thioethers with aromatic radical anions and (2) by using allylic or homoallylic alcohol groups on the receiving alkene. This type of reductive lithiation allows virtually any kind of organolithium to be generated, usually in a connective manner.
Cyclization by Intramolecular Carbolithiation of Alkyl- and Vinyllithiums Prepared by the Action of Aromatic Radical Anions on Phenyl Thioethers. High Stereoselectivity in the Cyclization Accelerated by an Allylic Lithium Oxyanion<sup>1</sup>
The reductivelithiation of alkyl and vinyl phenyl thioethers by aromaticradicalanions is shown to be the most general method yet known for preparing organolithiums capable of intramolecular carbometalation of unactivated alkenes to produce five-membered rings and in one case a four-membered ring (in a far higher yield than known cases). The relative rates of cyclization for alkyllithiums are secondary
Generation, rearrangements and some synthetic uses of bishomoallyllithiums
作者:Fangping Chen、Boguslaw Mudryk、Theodore Cohen
DOI:10.1016/s0040-4020(01)81201-1
日期:1994.1
bishomoallyllithiums rearrange to primary bishomoallyllithiums via cyclobutylcarbinyllithium intermediates. An oxyanionic group on a carbon atom adjacent to the lithium-bearing carbon atom has a remarkable accelerating effect on the ringclosure to a 4-membered ring. Formylation of some bishomoallyllithiums affords the precursors of type-II intramolecularenereactions, which generate six membered ring compounds
The superiority of properly prepared lithium 1-N,N-dimethylaminonaphthalenide (LDMAN) over other aromatic radical-anions for the generation of organolithiums by reductive lithiation
作者:Roman Ivanov、Ilan Marek、Theodore Cohen
DOI:10.1016/j.tetlet.2009.10.121
日期:2010.1
the far more widely used lithium p,p′-di-tert-butylbiphenylide (LDBB) in reductivelithiations by aromaticradical-anions to produce organolithium compounds, provided that careful temperature control is maintained during the generation of LDMAN. The main reason for the superiority is the great ease of separation of the aromatic byproduct dimethylaminonaphthalene by a dilute acid wash.
S-(+)-5-(Phenylthio)-2-pentanol and S-(+)-4-(Phenylthio)-2-butanol: Readily Prepared, Useful Additions to the Chirality Pool. Highly Enantioselective Syntheses of Naturally Occurring Spiroketal Pheromones
作者:Hong Liu、Theodore Cohen
DOI:10.1021/jo00112a025
日期:1995.4
The new chirons (S)-4-(phenylthio)-2-butanol (4) and (S)-5-(phenylthio)-2-pentanol (3) have been prepared efficiently in high enantiomeric excess by enzymatic reduction of the corresponding readily available ketones. Using the latter as a chiral building block, the highly optically enriched insect pheromonal components (5S,7S)-7-methyl-1,6-dioxaspiro[4.5]decane (7), (2S,6R)-2-methyl-1,7-dioxaspiro[5.5]undecane (8), and (2S,6R)-2-methyl-1,7-dioxaspiro[5.6]dodecane (9) have been synthesized in one pot by sequential deprotonation, reductive lithiation, transmetalation with cerium(III) chloride, treatment with lactones, and acidification.