Alkenyl and Alkynyl Anions

Dianions and Alkenyl and Alkynyl Anions.- Although the dilithiation of phenol was originally reported by Gilman some forty years ago, 

Metallated tertiary benzamides are useful precursors of poly-substituted benzoic acids. Benzamide (44 X = Br) reacts with an 

The successful us6 of the furan dianion (46) for the. synthesis of 2,5-disubstitutad furariB depends on the presence of TM.EDA during metallation. In the absen-ce of TMEDA, nucleophilic attack at the oxime may be observed., The course of the lithiation of furan- 

Several reports have appeared describing new applications of previously developed organolithium reagents. Thus, the dianion 

The direct -lithiation of 2-methoxypropenoic acid (59 X = OH) with Bu Li at -100 °C results in the formation of the dianion (60  

Dianions, Alkenyl, and Alkynyl Anions. - Problems have often been 

The free hydroxyl derivative (34) reacted smoothly to give the 

Further examples of the use of carbon dioxide as both a N-protecting group and for the stabilisation of a carbanion have 

The principal advantages of this methodology are the ease with which the protection and deprotection steps involving C02 are achieved. 

3-diketones with lactones as a general route into substituted 27 

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Carbanions are negatively charged organic species with an even number of electrons and the charge mainly concentrated on a carbon atom. In alkyl, alkenyl, and alkynyl anions all of the... 

Alkenyl and Alkynyl Anions.—In general, alkenyl-lithiums are generated by lithium exchange in alkenes however, in a useful alternative, alkyl- and aryl-... 

Group IV Alkenyl and Alkynyl Radical Anion ESR Data... 

Alkynyl anions are more stable = 22) than the more saturated alkyl or alkenyl anions (p/Tj = 40-45). They may be obtained directly from terminal acetylenes by treatment with strong base, e.g. sodium amide (pA, of NH 35). Frequently magnesium acetylides are made in proton-metal exchange reactions with more reactive Grignard reagents. Copper and mercury acetylides are formed directly from the corresponding metal acetates and acetylenes under neutral conditions (G.E. Coates, 1977 R.P. Houghton, 1979). 

Finally (d + aV dditions of 1-alkenyl and 1-alkynyl anions to carbonyl groups should be mentioned. Examples are the addition of vinylmagnesium bromide to ketones e.g. in the first step of Torgov s steroid synthesis (I.N. Nazarov, 1957), and the famous alkynylation of... 

As already mentioned in the introduction, anionic early transition metallocene complexes of the type [Cp2Zr(R1)(R2)(R3)] with R, R2, R3 = alkyl, alkenyl, or alkynyl, are unstable. Most of them exhibit electrostatic anion-cation pairing resulting in dimer, trimer, oligomer, or polymeric structures [21-25]. In marked contrast, stable 18 electron-zirconate complexes were prepared via a formal [3 + 2] cycloaddition reaction between 2-phosphino-zirconaindene 16a and alkyne derivatives (Scheme 5) [26,27]. 

The number of possible structural devices increases as functionality gets further from the anionic center in functionalized organolithium compounds. So, d-func-tionalized organolithium compounds can be classified according to the hybridization of the carbon atom bonded to the lithium in alkyllithium compounds (XXI and XXII), allylic and benzylic derivatives (XXIII-XXV) and alkenyl (XXVI-XXVIII) and alkynyl systems (XXK). 

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