Alkenyl and Other Unsaturated Derivatives

8 Alkenyl and other unsaturated derivatives. A C n.m.r. study of Bu C= C- Li in THF revealed 1 dimeric and 3 different tetrameric aggregates the tetramers probably only differ in number of THF molecules of solvation.  

Cyclo-octyne reacts with Li powder at -35 C in EtgO to give ci -l,2-Lig-cyclo-octene (stable at 40 C but with tj l h at RT) and 2,2-Lig-l,l -b1cyclo-octenyl in contrast, 3-octyne slowly provided the trans-adduct. The mechan- 

Bicyclo[3.2.1 ] octa-2,6-dienyl-lithium (21) has been isolated as the TMED adduct. A crystal structure determination of (21. TMED) indicated that Li is bound to the carbanion by both allylic and olefinic bonding. As TMED is also co-ordinated to Li, Li is 7 co-ordinated the MNDO structure of (21) shows overall agreement with the j(-ray structure of (21. TMED). N.m.r. spectra 

Rates of isomerisation of trans-neopentylallyl-M in THF increases in the sequence Li Na K. The crystal and solution structures of [PhS02CHLiCH=CH2. diglyme]2, from PhS02CH2CH=CH2 and BuLi in diglyme, have been investigated.  

In the crystal, there is a L1202S2 ring with a penta-co-ordinate Li (to 5 0) the allyl group lies outside the co-ordination sphere of Li. A homonuclear, 

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