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The diastereoselectivities of aldol reactions of 2-methylpropanal with various enolates of 5-O-methoxymethyl and 5-O-triethylsilyl derivatives of the four racemic diastereomers of 6-(2-ethyl-1,3-dioxolan-2-yl)-5-hydroxy-4-methylheptan-3-one are reported. Reactions of the (E)-enol dicyclohexylborinates, (Z)-enol 9-BBN borinates (i.e., 9-((Z)-enoxy)-9-borabicyclo[3.3.1]nonanes), Li (E)-enolates, Li (Z)-enolates, and Ti(IV) (Z)-enolates were examined. Boron and Li enolates were prepared by standard methods, but Ti(IV) enolates were obtained via transmetalation of the Li (Z)-enolates by reaction with TiCln(Oi-Pr)(4-n) (n = 0-2). Aldol relative topicity (simple diastereoselectivity) was strongly correlated to the enolate geometry: anti aldols from (E)-enolates and syn aldols from (Z)-enolates. However, for each enolate type, the diastereoface selectivities varied widely (by factors of 5-400) with the relative configuration and nature of the C5 protecting group in the 8 starting ketones. Plausible transition state models are postulated to rationalize some of these observations. The relative configurations for the complete set of 16 diastereomeric 2-(2-ethyl-1,3-dioxolan-2-yl)-7-hydroxy-3-(methoxymethoxy)-4,6,8-trimethylnonan-5-one aldol adducts were confirmed by NMR analysis of 12 acetonide derivatives prepared from the corresponding 5,7-syn diols. Examination of the NMR data for the above set of aldol adducts revealed consistent trends that were exploited to assign the relative configurations of 13 diastereomeric 2-(2-ethyl-1,3-dioxolan-2-yl)-7-hydroxy-3-(triethylsilyloxy)-4,6,8-trimethylnonan-5-one aldol adducts.

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Synthesis of Aryl Halomethylated Unsaturated Iminolactones (IV) -[via microwave assisted multi-component reactions under solvent free conditions]. -(ZONOUZI*, A.; RAHMANI, H.; BINIAZ, M.; IZAKIAN, Z.; NG, S. W.; J. Chem. Res. 35 (2011) 7, 412-415, http://dx.doi.org/10.3184/174751911x13099687368563 ; Sch. Chem., Coll. Sci., Univ. Tehran, Tehran, Iran; Eng.) -A. Forchert 02-102