Lithium 1-propenyl

Lithium, methyl, 55,7, 10 Lithium, phenyl-, 55,11 Lithium phenylthio(alkyl)cuprates, 55,122 LITHIUM, phenyltluo(fe/f-butyl)cuprate [Lithium, phenylthio( 1,1 -dimethyl-ethyl)cupiate, 55,122 Lithium, 1-propenyl-, 55, 111 LITHIUM, ( >l-propenyl-, 55, 103 Lithium thiophenoxide [Ben7enethiol, lithium salt], 55, 122... 

IITHIUM (E)- propenyl-, 55, 103 Lithium, 1-propenyl-, 55, 111 Lithium salts, complexes with macrocyclic ligands, 57, 78... 

Hence, for e.vo/e free energy of activation of AG 38, c of 17 keal/mol was found, with a half-life period of 8 minutes at this temperature17. 

Deprotonation of alkenes by butyllithium in the presence of TMEDA affording, for example, 2-propenyllithium from propene14, (2-methyl-2-propenyl)lithium from 2-methylpropene31,... 

In ( )-[2-(l-propenyl)-l, 3-dithian-2-yl]lithium, no problem of EjZ selectivity arises. It is easily prepared by deprotonation of the allylic dithiane87,88 with butyllithium in THF, whereas deprotonation of the 2-propylidene-l, 3-dithiane requires the assistance of HMPA. The addition to saturated aldehydes proceeds with excellent y-regioseleetivity and anti selectivity88,89. As often observed in similar cases, aldehydes which bear an, p2-carbon atom adjacent to the carbonyl group give lower selectivities. The stereoselectivity decreases with ketones (2-bu-tanone y/a 84 16, antiisyn 77 23)88. The reaction with ethyl 2-oxopropanoate is merely nonstereoselective90, but addition of zinc chloride improved the syn/anti ratio to 96 4, leading to an efficient synthesis of ( )-crobarbatic acid. 

An interesting case of product-controlled simple diastereoselectivity has been reported103. [l-[Methyl(nitrosoamino)]-2-propenyl]lithium adds to benzaldehyde at — 78°C to give the amino alcohol with an anti/syn ratio of 65 35, but equilibration of the reversible reaction at room temperature leads exclusively to the more stable, vv -product. 

The nucleophilic alkenoylation of a-phenyl-substituted aldehydes and ketones with (methyl-substituted) [l-cyano-l-(trimethylsilyloxy)-2-propenyl]lithium proceeds with good 1,2-induction to afford the j> i-hydroxy ketones109. 

Racemic [l-(4-methylphenylsulfinyl)-2-propenyl]lithium, prepared with lithium diiso-propylamide in THF, adds to racemic chiral 2-methylalkanals with good a- and syn selectivity114, us Qn heating with trimethyl phosphite or triethylamine, the major isomer furnishes the ( )-.yvn-2-alkene-l,4-diol by Mislow rearrangement1 lb. 

To a solution of 5 mmol of 1,3-diphcnyl 3-[(S )-2-mcthoxymethyl-l-pyrrolidinyl]-2-propenyl[lithium in 10 mL of tort-butyl methyl ether (prepared according to Section D. 1.1.1.2.2.3.) at 0°C. 6.25 mmol of the aldehyde (and eventually 6.25 mmol of lithium halogenide in 27 mL of leri-butyl methyl ether) are added dropwise. Stirring is continued for 2 h and 0.39 g (5.0 mmol) of acetyl chloride are added. After 2 h stirring at r.t., 10 mL of the solvent, 50 mL of diethyl ether and 10 mL of 2 N aq hydrochloric acid are added and stirring is continued for 2 h at 20 C. The organic layer is extracted with three 20 mL-portions of water and the aqueous solutions are reextracted with diethyl ether. The combined aqueous solutions are dried over Na,S04, concentrated in vacuum and the residue distilled to yield a mixture of xyn- and on/i-ketones >90% ee, determined by H-NMR with Pr(hfc)3. 

Addition of anhydrous magnesium bromide to [l,3-bis(trimethylsilyl)-2-propenyl]lithium improves the antijsyn selectivity of the reaction with benzaldehyde from 80 20 to 94 6 23. 

These reagents are not isolated but are used directly in reactions with aldehydes, after generation of ate complexes via the addition of an alkyllithium reagent or pyridine11. 2-(2-Propenyl)-1,3,2-dioxaborolane is also metalated upon treatment with lithium tetramethylpiperidide, but mixtures of a- and y-substitution products are obtained upon treatment of this anion with alkylating agents20. Consequently, this route to a-substituted allylboron compounds appears to be rather limited in scope. 

Diisopropylamino(dimethyl)silyl]-2-propenyl]lithium adds to aromatic and x-branched aldehydes in the presence of anhydrous zinc chloride with essentially complete anti stereoselectiv-ity3s. as expected from the chair-like pericyclic transition state formed by the ( -intermediate. The addition products are not isolated, but after O-silylation, oxidative desilylation with retention of configuration forms the rmft-diols. 

Trimethylsilyl)-2-propenyl]zinc chloride in four-fold excess, generated in situ from the lithium compound by addition of anhydrous zinc chloride, reacts with chiral ketones, e.g., 2-bor-nanonc, to form the ( )-vinylsilanes with high y-regio- and induced diastcreoselectivity44,45. 

The lithium enolates of cyclopentanone and cyclohexanone undergo addition-elimination to the 2,2-dimethylpropanoic acid ester of ( )-2-nitro-2-hepten-l-ol to give 2-(l-butyl-2-nitro-2-propenyl)cycloalkanones with modest diastereoselection. An analogous reaction of the enolate ion of cyclohexanone with the 2,2-dimethylpropanoic acid ester of (Z)-2-nitro-3-phenyl-2-propenol to give 2-(2-nitro-l-phenyl-2-propenyl)cyclohexanones was also reported. The relative configuration of these products was not however determined6. 

In small-scale experiments, overnight reaction of lithium dipropenylcuprate with lodobpnzene m ether containing 20 equivalents of pyridine at 25° gave 1-propenyl-benzene in 60 % yield. For couplmg with aromatic halides, this solvent system is superior either to ether-tetrahydrofuran or to ether containing 4 equivalents of hexamethylphosphonc triamide. 

The lithium derivative of di-f-butylfluorosilyl-2,6-diisopropylphenyl-amine reacts with 2-methyl-2-propenal in two competing ways. In a [2 + 4] cycloaddition, an oxa-3-aza-2-sila-5-cyclohexene is formed and in a [2 + 2] cycloaddition, 2-methyl-2-propenyl-Af-(2,6-diisopropylphenyl)-imine is generated via an (SiNCO)-ring intermediate.18 36... 

Scheme 10. Total synthesis of artemisinin by Schmid and Hofheinz. Conditions (i) ClCH20Me, PhN(CH3)2, DCM, rt. (ii) B2H6/THF, H2O2 (iii) PhCHzBr, KH, THF/DMF (iv) HCl, MeOH (v) PCC, DCM, rt. (vi) LDA, (E)-(3-iodo-l-methyl-l-propenyl)-trimethylsilane (vii) lithium methoxy(trimethylsily)methyhde (viii) Li/NH3 (ix) PCC DCM (x) m-CPBA, DCM (xi) -Bu4NF, THF, rt. (xii) O2 (methylene blue, DCM, rt.) (xiii) HCOOH, DCM.

From equation 10 with phenyl lithium as the benchmark species, RLi, and the hydrocarbon compounds, R H, in their reference gaseous states, the derived enthalpies of formation of allyl, ii-l-propenyl, 2-propenyl and ethyl lithium, are —12.8, —7.3, 54.3 and —58.3 kJmoP, respectively. The first and last of these are remarkably consistent with the values in Table 1. 

The present method offers a more efficient and convenient two-step route to the parent a,B-unsaturated acylsilane derivative. The first step in the procedure involves the conversion of allyl alcohol to allyl trimethylsilyl ether, followed by metalation (in the same flask) with tert-butyllithiura at -75°C. Protonation of the resulting mixture of interconverting lithium derivatives (2 and 3) with aqueous ammonium chloride solution furnishes (1-hydroxy-2-propenyl)trimethylsilane (4), which is smoothly transformed to (1-oxo-2-propenyl)trimethylsilane by Swern oxidation. The acylsilane is obtained in 53-68% overall yield from allyl alcohol in this fashion. 

In an approach to direct the alkylation of (l-silyl-2-propenyl)lithium into the a-position by chelating substituents on the silicon atom, chiral pyrrolidinyl-substituted allylsilane 1 was deprotonated and alkylated with iodomethane (94%)51. Regiocontrol was moderate, the a-product 2 dominating (85%). 

A number of other a-amido boronic esters or adds have been synthesized similarly and are of interest as enzyme inhibitors45,63,64. It is noteworthy that the substitution of an (S)-pinanediol (1-chloro-2-propenyl)boronic ester with lithium hexamethyldisilazanide to form the (S)-pinanediol [l-bis(trimethylsilyl)amino-2-propenyl]boronic ester proceeds without difficulty, in contrast to the unsuccessful attempts to react (S)-pinanediol (l-chloro-2-propenyl)boronic esters with alkoxides (Section 1.1.2.1.3.4.)16. 

Methoxy(phenylthio)-trimethylsilylmethyllithium, 182 l-Methoxy-3-phenylthio-3-trimethyl-silyl-l-propenyl-3-lithium, 182 Methyl (trifluoromethylsulfonyl)methyl sulfone, 193... 

Methoxy(phenylthio)trimethylsilyl-methyllithium, 182 l-Methoxy-3-phenylthio-3-trimethyl-silyl-l-propenyl-3-lithium, 182 1 -Methoxy-4-(trimethylsilyl)-1 -butene-3-ynyl-2-lithium, 180 Methyllithium, 142, 188, 203, 214, 315 Methyllithium-Methylaluminum bis-(2,6-di-t-butyl-4-methylphenoxide), 203... 

Katritzky, A. R. Li, J. Malhotra, N. N-Vinyl, N-allyl, N-propenyl and N-propargylbenzotri-azoles reactions of their lithium derivatives. Liebigs Ann. Chem. 1992, 843—853. 

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