The Neighboring Heteroatom Effect Unique To The Aqueous Organic Reactions And Its Applications

In this dissertation, the aqueous aldol reactions and Darzens reactions have beenreported. The advantages of the aqueous reactions over the organic solvent-mediatedones have been revealed according to the control experiments.Very sparingly soluble high-melting-point (VSSHMP) steroidal ketones,aromatic aldehydes, base, Aliquat336, water and granular polytetrafluoroethylene(PTFE sand) were mechanically stirred by a modified stirring rod designed by us andten aldol products,β-unstatured ketones were obtained in quantitative yields. Inthese aqueous aldol condensations, Aliquat336functions as both a phase transfercatalyst (PTC) and a reaction medium. In these reactions, the neighboring heteroatomeffect (NHE), which is unique to the aqueous systems and not applicable to theorganic solvent systems according to two series of control experiments, has beendemonstrated for the first time. In the M2CO3-catalyzed aqueous aldol reactions ofneighboring heteroatom-bearing ketones, the weakest but the hardest base Li2CO3wasthe most efficient catalyst. The NHE was further applied in the aqueous aldolreactions with the neighboring heteroatom-bearing ketones and protected aldosylhemiacetals and in the aqueous Darzens reactions with halocarbonyl compounds.Several advantages of these aqueous reactions over the organic solvent-mediated oneshave also been demonstrated including higher yields, shorter reaction times, simplerpurifications and better functional group tolerance.In the aqueous aldol condensations with heteroatom-bearing aliphatic ketones,the weak base Li2CO3was an efficient catalyst and therefore base-liable groups suchas epoxides, esters and silyl groups could survive. Twenty,β-unstatured ketoneswere synthesized from these aqueous reactions in up to quantitative yields. In thecontrol experiments, aldol reactions with epoxyketones catalyzed by weak and strongbases in organic solvents all ended in failure. The LiOH-catalyzed aqueous directaldol reactions of heteroaromatic ethanones and alphatic aldehydes, which were alsofailed in organic solvents according to the control experiments, were accomplishedwithout PTC, and gave eight β-hydroxyketones in moderate to excellent yields and inlarge scales in some cases. In the literatures, these aldol reactions have necessarilybeen conducted using stoichiometric strong base at a low temperature and in an inertatmosphere. The LiOH-and TBAB-catalyzed aqueous condensations of protectedaldosyl hemiacetals with ketones all ended in15min and twelve carbohydratederivatives were synthesized. The aliphatic ketones led to chiral conjugated dienones and the aromatic ketones1,5-dicarbonyl compunds with a new carbohydrate-derivedskeleton. When liquid ketones were used, the excess starting materials andby-products were removed under reduced pressure, and therefore quantitative yieldsof desired products were obtained with further purifications avoided. In these aqueousaldol reactions, the water, base, PTFE sand and PTC all could be recyclable.In the aqueous Darzens reactions of simple halocarbonyl compounds, some ofwhich were ended in several minutes, Li2CO3or LiOH was the base and sodiundodecyl sulfate or Aliquat336the PTC. These aqueous reactions, from which sixteen,β-epoxycarbonyl compounds were synthesized, have higher yields and shorterreaction times over the orgainc solvent-mediated ones according to the controlexperiments. In the aqueous Darzens reactions with enantiomeric pure halosteroidalketones, the memory of charity was observed for the first time in aqueous systems andtherefore twelve chiral epoxyketones were synthesized in water.