Diethyl ketone, selective synthesis

This reaction is observed as a side reaction of hydroformylation. With ethylene the formation of diethyl ketone can be optimized to give high product selectivities, however, with higher, especially unsymmetrically substituted alkenes, only low ketone product selectivities and re-gioselectivities are observed. Thus, the reaction is only rarely applied to open chain ketone synthesis and little information is available about the stereochemistry of this reaction type1 -3. 

Aldol Reactions. sjw-Aldol adducts can be formed enantio-selectively from the reaction of diethyl ketone and various aldehydes using bromoborane R,R)- as a chiral controller (eq 7). Reactions typically proceed in 85-91% yield with >95% ee. This process led to the highly efficient synthesis of the rice and com weevil aggregation pheromone sitophilure 19 (R = C2H5). Here the bis(tosyl)amide was easily recovered in high yield, since the aldol products were soluble in hexanes, but the chiral backbone... 

Alkenyl, Alkynyl, Aryl and Related Acids. Vinylphosphonates are an important group of compounds that have found use in organic transformations. They are also useful reagents for the synthesis of biologically active systems. The synthesis of vinylphosphonates is varied. However additional convenient routes to them are always welcome. Four recent reports demonstrated that zirco-nacycles (180), readily available from diethyl 1-alkynylphosphonates, are very useful precursors of different vinylphosphonates. They react with alkynes, aldehydes, ketones acyl chlorides and nitriles to produce, in a highly stereo- and regio-selective manner, substituted vinylphosphonates (181), (182), (183) (184) and (185) respectively (Scheme 46). 

Direct alkylation of hydrazine itself with halides and sulfates usually gives mixtures of mono- and poly-alkylated hydrazines. It is possible to get useful yields of the monoalkylhydrazine by using an excess of hydrazine. Several specific procedures leading to monoalkylhydrazines are based on selective alkylation of hydrazine derivatives with protecting groups attached. So, easily prepared acetone N-(diethoxyphosphoryl)hydrazone (75) can be used. Phase-transfer catalyzed N-alkylation of (75), followed by deprotection with p-toluenesulfonic acid provides monoalkylhydrazine sulfonates (76 Scheme 17). Similarly, N-alkyl-N-arylhydrazines have been prepared by phase-transfer catalyzed N-alkylation of arylhydrazones (Scheme 18). An efficient, one-pot method for the synthesis of a variety of polysilyl-ated hydrazines employs hexamethyldisilane (equation 30). Polysilylated hydrazines were found to react with aldehydes or ketones to give hydrazones under anhydrous conditions. By treatment with triphenylphosphine and diethyl azodicarboxylate primary and secondary alcohols can be converted to hy-dr ine derivatives (equation 31). ... 

The protected butane-1,2,3,4-tetraol 15, easily available in three steps from D-tartaric add diethyl ester, was the starting material for the synthesis of (+)-phomopsohde B (Scheme 2.4). Thus, IBX (2-iodoxybenzoic acid) oxidation of the primary alcohol followed by HWE olefination with a chiral phosphonate derived from L-lactic add (not depicted) gave a,fi-enone 16. Stereoselective reduction of the ketone carbonyl and acidic deavage of the acetal moiety furnished triol 17. Selective protection of the two secondary hydroxyl groups was achieved through triple silylation with subsequent selective desilylation of the primary OTBS group. 

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