Allyllithium reagents

Allyllithium reagents have also been used in the synthesis of (Z)-y-alkoxyallylboronates 23 2 5. Stereoselectivity is excellent in these reactions since the (Z)-y-alkoxyallyl carbanions prepared by metalation of allyl ethers are stabilized by chelation. The (Z)-y-alkoxyallyl(diisopinocam-pheyl)boranes are prepared at low temperature by an analogous procedure and must be used at — 78 "C otherwise reaction diaslereoselectivity suffers owing to the facile isomerization to the -isomer26. 

Haynes et al.3 have examined the effect of HMPT on the reaction of arylthio-allyllithium reagents with cyclopentenonc. In THF alone the reaction leads mainly to 1,2-adducts, derived from both - and /-substitution. However, when the same... 

Reductive lithiation of allyl phenyl sulfides.1 This reagent is particularly useful for preparation of allyllithium reagents at temperatures at which the anions are stable. Moreover, regioselectivity in reactions can be achieved by conversion to allyltitanium(IV) complexes by metal exchange with Ti(0-/-Pr)4. Thus the un-symmetrical anion formed from the allyl sulfide 1 with LDMAN reacts with cro-tonaldehyde to give a mixture of 1,2- and 1,4-adducts. The 1,2-adduct 2 can be obtained in high yield as two diastereomers (9 1) by use of the allyltitanium complex (equation I). 

The effect of the counter cation (Table XI) may be in a manner similar to those proposed for alkyllithium and allyllithium reagents. 

Mauze has examined the reactions of chlorine-bearing allyllithium reagents with imines to produce 2-alkenylaziridines <80JOM(202)233, 84TL843). 

Allyllithium reagents may be prepared directly from the hydrocarbon with the strong base combination, butyllithium and TMEDA [35]. These complexed reagents give high yields too, when used in two-fold excess with primary halides. 

Mixed cuprates derived fiom deprotonation and transmetalation of ketone dimethylhydrazones, using copper(I) thiophenoxide as the copper(I) source, are effective as enolate equivalents in 1,4-conjugate additions to a,3-unsaturated esters. The mixed phenylthio cuprate was found to exhibit approximately the same selectivity and reactivity in these reactions as a similar homocuprate (63) prepaid from the aza-allyllithium reagents and copper(I) iodide (equation 29). 

Aza-allyllithium reagents are of interest in synthesis, and on account of their stereoisomerism. The structure of the diethyl ether adduct of N-(2,2-dimethyl-l-methylenepropyl)-N-... 

Katzenellenbogen, J. A., and R. S. Lenox The generation of allyllithium reagents by lithium-tetrahydrofuran reduction of allylic mesitoates. A new procedure for selective allylic cross coupling and allylcarbinol synthesis. J. Org. Chem. 38, 326—335 (1973). 

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