Alkenyl aryllithiums

The cascade sequence that affords bicyclic systems fails with the lithium derivatives of 2-bromo-iV,iV-diallylaniline. The methodology is useful for the synthesis of 3-substituted indolines and indoles, but the substrate undergoes only one anionic cyclization. Alkenyl vinyllithiums and alkenyl aryllithiums have also been employed in the preparation of alkylidenecyclopentanes and indanes. The intramolecular addition of vinyllithium reagents... 

On the other hand, alkenyl aryllithiums can undergo diastereoselective cyclizations in very good yields. Pedrosa and coworkers163 reported that chiral 2-(o-bromophenyl)-substitutedperhydro-l,3-benzooxazines 281, initially transformed to the aryllithium derivative, gave the intramolecular 6-exo carbolithiation reaction with unactivated double bonds attached to the nitrogen substituent of the heterocycle (Scheme 87). By adding 2 equivalents of TMEDA to the aryllithium derivative 1,3-benzooxazines 281 prepared at —90 °C,... 

The action of chloroamine and bromoamine on organometallic reagents has been reviewed102 and a comprehensive review of electrophilic aminations of carbanions has appeared103. Alkyl, alkenyl and aryllithium compounds are converted into tertiary amines 84 by reaction with the mesityl compounds 83 (R2 = Me or Et Ar = 2,4, 6-MesCeHj)104. 

Organolithium additions. Alkyl-, alkenyl-, and aryllithiums can react as potent nucleophiles in the presence of BF, etherate. Thus epoxides and oxetanes are rapidly alkylated by reaction with an organolithium and BF, etherate (2 equiv. of each) at —78°. Examples ... 

BF3 Et20 facilitates the addition of moderately basic nucleophiles like alkyl-, alkenyl-, and aryllithium, imines, Grignard reagents, and enolates to a variety of electrophiles. 

Cyclopropanone acetals with a quaternary carbon atom in chiral form can be established by addition of bisoxazoline-ligated allylzinc reagents to the cyclopropenes.The t-BuLi/(-)-sparteine combination favors Br-Li exchange and also promotes enantioselection in the intramolecular addition of aryllithium to an o-alkenyl side chain (e.g., indoline synthe-j.ijj) I28.I29 Moderate asymmetric induction is shown in the hydroarylation of norbomene in the presence of 63. 

With Mel or dimethylsulfate, the methyl derivatives are prepared with acetyl chloride-Cnl or the Weinreb amides, the ketones with methyl chloroformate, the methyl esters and with dialkyl oxalate, the a-oxo esters. Alkyl long-chain derivatives are better prepared by lateral (benzylic) metalation (see Section 26.7). Besides, aryllithiums may undergo transmetalation to afford a large panel of organometaUic species (Li Zn, Cu, Sn, Si, B, etc.), key reactants for transition metal-catalyzed reactions. The cross-conpling of aryllithium reagents with alkenyl triflates in the presence of the commercially avaUable catalytic system [Pdjfdbaljl/DavePhos] was recently reported [40]. 

The sulfonation of polar organometallics with sulfur trioxide has only scarcely been investigated. Quite satisfactory results have been reported when alkyl-, 2-alkenyl-, or (het)aryllithiums, bearing or not functional groups, are treated with the trimethylamine complex of sulfur trioxide. Acidification provides the sulfonic acids RSO3H in a straightforward manner. 

Lithium A number of Michael-type additions of organolithiums have been described. This is also the case of the reaction of aryllithiums with nitroalkene (389). Deprotonation of the benzylic fluoride (455) with LDA, directed by the neighbouring sulfoxide group, generated the benzyllithium intermediate (456), which underwent addition to the Michael acceptor R CH=CHY (Y = CO2BU, S02Ph R = Ar, alkyl, alkenyl) in a diastereoselective manner controlled by the chiral sulfur to afford the 5yn-configured product (457) with <99 1 dr ... 

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