[3002-94-6] · C3H5Li · Cyclopropyllithium · (MW 48.02)
(organolithium reagent used in the synthesis of a variety of cyclopropyl derivatives,2 five-membered ring nitrogen heterocycles via cyclopropylimine rearrangement,3 and cyclopentenes via vinylcyclopropane rearrangement4)
Alternate Name: lithiocyclopropane.
Solubility: sol pentane and ether.
Form Supplied in: solution in pentane or ether.
Preparative Methods: cyclopropyllithium is usually prepared as a solution in ether by reacting highly dispersed Lithium with cyclopropyl chloride7 or bromide.8 The reaction can also be conducted in pentane.2 Transmetalation methods have also been described.7b,9
Handling, Storage, and Precautions: solutions of organolithium reagents are highly flammable and moisture sensitive. Appropriate precautions are recommended. Use in a fume hood. Stability of cyclopropyllithium in ether is similar to that of n-Butyllithium, whereas in THF its stability is greater.8a
Cyclopropyllithium reacts readily with common electrophiles to form a variety of compounds containing a cyclopropyl group. Thus reaction with aldehydes10 and ketones2,11 leads to secondary and tertiary alcohols respectively (eqs 1 and 2).11a
Two- and three-carbon homologations have been realized by using ethylene oxide7a and oxetane8b as electrophiles. Reaction with vinyl-substituted epoxides (eq 3) constitutes an example of four-carbon homologation.12
Cyclopropyllithium condenses in a typical fashion with carboxylic acids to give cyclopropyl ketones,13 and a controlled reaction with N-Formylpiperidine leads to cyclopropylcarbaldehyde in 75% yield.14 Cyclopropyllithium also adds to carbon-nitrogen multiple bonds. Thus addition to imines leads to amines15 while reaction with cyanopyridines yields ketones in good yields (eq 4).16
Cyclopropyllithium has also been used in the synthesis of cyclopropylpyridines,12 Cyclopropyltriphenylphosphonium Bromide,18 cyclopropyl phosphines,19 silanes19,20 and organogermanium compounds.21
Addition of cyclopropyllithium to a-piperidinocyclopropanenitriles leads to the intermediate imines which subsequently undergo acid catalyzed rearrangement to form nitrogen heterocycles in moderate yields. Different products can be obtained depending on the kind of acid used (eq 5).3,22
A mixed cuprate prepared in situ from cyclopropyllithium and PhSCu readily displaces iodide in b-iodocyclopentenones to give the substitution products in high yields. The latter undergo thermal ring expansion, providing an interesting method for cyclopentene annulation (eq 6).4
Cis and trans 1-lithio-2-methoxycyclopropanes (1) were prepared by lithium-halogen exchange reaction from corresponding bromides and condensed with aldehydes to give the addition products which readily undergo acid-catalyzed rearrangement to b,g-unsaturated aldehydes.23
Both 1-lithio-1-methyl-2-vinylcyclopropanes (2) and 1-lithio-2-vinylcyclopropanes (3) (cis and trans) were prepared in similar fashion and subsequently applied to cycloheptane annulations.24,25 These and other substituted cyclopropyllithium reagents are configurationally stable.26
See also 1-Bromo-1-lithio-2-phenylcyclopropane; Cyclopropylmagnesium Bromide; 1-Lithio-1-methoxycyclopropane; Lithium Cyclopropyl(phenylthio)cuprate.
Harry M. Walborsky & Marek Topolski
Florida State University, Tallahassee, FL, USA