A novel homochiral magnesium bisamide base system has been prepared and reacted with a series of prochiral ketones in the presence of TMSCl to give efficient formation of the corresponding enol ethers in enantiomeric ratios of up to 95+5.

Reaction of (R,RЈ)-or (S,SЈ)-bis(1-phenylethyl)amine with n BuLi in hexane solution gave the chiral amide [{PhC(H)Me} 2 NLi] 1. Complex 1 crystallises with approximate D 3 symmetry as a ring trimer (1 3 ) from hexane solution, as determined by X-ray crystallography. In direct contrast to the crystal structure of the related compound dibenzylamidolithium, [{(PhCH 2 ) 2 NLi} 3 ], no significant agostic Li ؒ ؒ ؒ C(H) contacts are present in 1 3 . Solution 1 H and 7 Li NMR spectra of 1 in d 8 -toluene show the presence of two distinct aggregated species which have been assigned as a trimer and a monomer. The complex [PhCH 2 {PhC(H)Me}NLiؒTHF] 2ؒTHF, was prepared by reaction of n BuLi with (R)-N-benzyl-α-methylbenzylamine in a hexane-THF solution and has been determined by X-ray crystallography to adopt a dimeric structure (2 2 ؒ2THF) in the solid state with C 1 symmetry. As in 1 3 , no short Li ؒ ؒ ؒ C(H) contacts are present in 2 2 ؒ2THF. The lack of Li ؒ ؒ ؒ C(H) interactions in both 1 3 and 2 2 ؒ2THF suggests that the rotameric conformations adopted for the benzyl groups in the complexes are governed mainly by steric effects. Using ab initio molecular orbital calculations (HF/6-31G*), the minimum energy structure for unsolvated monomeric 1 1 was determined to be a C 2 symmetric molecule, I, where the faces of both phenyl groups are directed towards the metal, maximising the Li-aromatic π interactions. The related C 2 symmetric molecule with both methyl groups directed towards the metal is 8.68 kcal mol Ϫ1 less stable than I. Therefore, in the absence of aggregation and external solvation, significant stabilisation is achieved through Li ؒ ؒ ؒ C(H) benzyl interactions. The energy barrier to rotation for one benzyl sidearm for geometry I is 4.76 kcal mol Ϫ1 , representing a significant lifetime for this conformer.

Have it both ways: Enantiomerically enriched E vinyl glycines may be accessed from aldehydes in a concise sequence that combines an organocatalytic α sulfenylation, stereoselective olefination, a sulfimidation, and a [2,3] sigmatropic rearrangement (see scheme, Boc=tert‐butoxycarbonyl, nHex=n‐hexyl). Either enantiomeric series can be accessed by control of the alkene geometry in the olefination step.

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The cobalt carbonyl mediated cyclotrimerization of alkynes to yield both arenes and "flyover" complexes (which contain a C 6 Co 2 ring) has been reexamined with particular regard to the intermediacy of cobaltacyclopentadienes. Since the latter can now be obtained in controlled fashion from (alkyne)Co 2 (CO) 6 and can react with a third alkyne under mild conditions by using trimethylamine-N-oxide as promoter, the incorporation of three different alkynes into both arenes and flyovers has become possible. Cobaltacyclopentadienes, like their precursors, catalyze alkyne cyclotrimerization, but flyovers do not do so under comparable conditions and hence are not on the main reaction path to arenes. In some circumstances cleavage of cobaltacyclopentadienes must occur to account for the observed arene products. Crystal structures of two flyover complexes are reported.