Cyclopropyllithiums

Other 17a-substituted derivatives are obtained from l7-ketones and benzyimagnesium chloride/ allylmagnesium bromide,vinyllithium and cyclopropyllithium. ... 

Cyclopropane synthesis, 107 Cyclopropyllithium, 64, 72 17a-Cyclopropyl-3-niethoxyestra-l, 3,5 (10)-trien-17 -ol, 72... 

Other organometallic compounds that are hydrolyzed by water are those of sodium, potassium, lithium, zinc, and so on, the ones high in the electromotive series. Enantioselective protonation of lithium enolates and cyclopropyllithium compounds have been reported. When the metal is less active, stronger acids are required. For example, R2Zn compounds react explosively with water, R2Cd slowly, and R2Hg not at all, though the latter can be cleaved with concentrated HCl. How-... 

A three-step protocol has been applied to obtain homoallylic carbanions from cyclopropylmethanol derivatives by regioselective opening of intermediate cyclopropyllithiums. ... 

Diphenylsulfonium cyciopropanide has been generated irreversibly Method A, by reaction of triphenylsulfonium tetrafluoroborate with cyclopropyllithium in tetrahydrofuran at — 78°C 61,65 or Method B, by treatment of cyclopropyldiphenylsulfonium tetrafluoroborate with sodium methylsulfinylmethanide in 1,2-dimethoxyethane at —40°C.57,65 However, reversible formation from cyclopropyldiphenylsulfonium tetrafluoroborate with Method C, powdered potassium hydroxide in dimethyl sulfoxide at + 25 °C, is easier to perform and gives higher yields of cyclobutanones l.62 A large-scale preparation of cyclopropyldiphenylsulfonium tetrafluoroborate has been reported.65,66... 

Table 12. Addition of l-(Methoxymethoxy)cyclopropyllithium and 1-Ethoxycyclopropyllithium to Saturated and Unsaturated Carbonyl Compounds. Rearrangement to Cyclobutanones and Vinylcyclobu-tanones...

The related lithium(phenylthio)cyclopropylcuprate, prepared from cyclopropyllithium and PhSCu, has been extensively used in the synthesis of /1-cyclopropyl enones by coupling with the corresponding fl-iodo enones (equation 10)34 36. Repetitive regioselective coupling of ethynylcyclopropane units by this method led to polyspirocyclopropyl acetylenes as precursors to [NJpericyclynes37. 

Bis(cyclopropyl)titanocene is prepared from cyclopropyllithium and dichloroti-tanocene in 95% yield. The complex has been utilized as an olefination reagent in reactions with a wide variety of carbonyl compounds, including esters, furnishing the corresponding methylenecyclopropane derivatives (equation 13). ... 

The square pyramidal complexes of group 9 iridium cyclopropylbis(>/4-diene) complexes were recently synthesized in poor yields (3-5%) by metathesis reaction between (tf-diene)2 IrCl and cyclopropyllithium or cyclopropylmagnesium bromide (equation 16)45. 

While the first transition metal carbene complex was reported in 1964134, the first cyclopropylcarbene complex salt [(CO)5Cr=C(chromium hexacarbonyl, followed by tetramethylammonium bromide135. Subsequent reaction with trimethyloxonium fluoro-borate gave methoxycarbene complex (CO)5Cr=C(OMe)(c-Pr) (equation 62)136. 

F urthermore, the lithium acetylides could be trapped with a large variety of electrophiles to yield a plethora of 2-substituted (l-chlorocyclopropyl)acetylenes, as shown in equation 156 for l-chloro-2,2,3,3-tetramethyl-l-ethynyl-l-cyclopropyllithium. 

Alkyl(aryl)halonium Ions. Dence and Roberts366 attempted to prepare the cyclopropylphenyliodonium ion from phenyliodoso chloride and cyclopropyllithium [Eq. (4.104)]. However, they were unable to obtain the corresponding iodonium ion or any cyclopropylbenzene from the reaction mixture. Thus, the iodonium ion was not formed, even as an unstable reaction intermediate. 

Lithium (cyelopropyl)(phenylthio) cuprate (l).27 This cuprate is prepared by addition of cyclopropyllithium to phenylthiocopper in THF at -78- — 20°. It converts /J-iodo enones (2) into /1-cyclopropyl enones (3) in excellent yield, even when 2 is substituted at the a-position by a methyl group. The products are useful because they rearrange when heated to annelated cyclopentenes (4 and/or 5). The rearrangement is particularly efficient when R = H, and results in 5 as the major product ( 85% yield). 

Another 1,2-silyl migration from C to C was found during the reaction of an a-silyl cyclopropyllithium 42 with dichloromethyl methyl ether 43 to give the silyl ketone 44 (equation 36)87. 

Corey exploited the remarkable configurational stability of cyclopropyllithiums in his synthesis of hybridalactone. The stannane 28 was made by Simmons-Smith cyclopropanation of the allylic alcohol 27 and resolved by formation of an O-methyl mandelate ester. Transmetallation of 29 with 2 equiv. BuLi gave an organolithium which retained its stereochemistry even in THF over a period of 3 h at 0 °C, finally adding to 31 to give 32. 

The amide-substituted cyclopropyllithium trans-33 is configurationally stable at -78 °C, but epimerises to the more stable, chelated cis diastereoisomer on warming to 0 °C.19... 

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