Selective Reactions with Organoaluminum Compounds

Abstract

With the aid of selected examples an overview is given of the development trends in highly discriminative reactions using organoaluminum compounds. 1) Isomerization of substituted oxiranes into allyl alcohols has been effected both stereo-and regioselectively by means of a new organoaluminum reagent, diethylaluminum 2,2,6,6-tetramethylpiperidide (DATMP); this reaction which provides a new route for the regiospecific transformation of allyl alcohols into 1,3-dienes. 2) A novel nonenzymic heterolysis of allylic phosphates of terpenoids has been effected by organoaluminum compounds and has enabled development of a new method for the selective synthesis of cyclic terpenes.3) The reductive condensation of a-haloketones with carbonyl compounds in the presence of diethylaluminum chloride and zinc affords 8-hydroxycarbonyl derivatives in good yields with exclusion of undesired self-condensations products.

Organic Reactions in the Solid State: The reactivity of guest molecules in tri‐o‐thymotide clathrates

“…The two reactions involving the prochiral substrates 8 and cyclohexadiene (19) demonstrated the occurrence of chirality transfer from the cage onto the product. The most representative reaction was the two-step conversion of 8 by cage-specific allylic isomerization to cyclohex-2-en-1-01 18 followed by the nucleophilic substitution of OH by C1 (Step C) to furnish 17 in 100% yield (by 'H-NMR; Scheme 4 , a ) .…”

“…Depending on the substrate, either one of two paths were then observed: addition of the hydrogen halide to the double bond to form a halohydrin (Step B ) or nucleophilic substitution of the OH group leading to an CQ -unsaturated halide (Step C). By way of contrast, in solution, strongly basic reagents [7], Lewis acids [8], or vitamin B,, in catalytic amounts [9] led to allylic alcohols. Isomerization by heterogeneous catalysis with solid acids or bases also proved to be practicable [lo].…”

Silyl enol ethers and silyl ketene acetals

“…The reactions of other homologues 1 8 2 , such as (93), (94) and (95), with simple dienophiles have been reported; combination of the diene (96) with methyl dichlorophosphine yields 18 3 the bicyclic 3-phospholanone (97) (Scheme 17.116). Interestingly, the diene (93) is reportedly obtained from cyclohex-2-enone under either kinetic or thermodynamic conditions The regiospecificity of the diene (98) in cycloaddition is displayed further in its reaction 188 with the quinone juglone (102) unique products being formed in each case (Scheme 17.119).…”

Synthesis of (E)‐α‐Hydroxy‐β,γ‐Unsaturated Amides with High Selectivity from α,β‐Epoxyamides by Using Catalytic Samarium Diiodide or Triiodide

“…The isomerisation of oxiranes1 to allylic alcohols is a valuable transformation in organic synthesis and has been accomplished by a variety of reagents including 1) organoselenium compounds,2 2) dialkylaluminum amides,3 3) alkylboron trifluoromethanesulfonates,4 4) silyl iodides,5 5) boron trifluoride etherate6 and 6) various dialkylamides 7. These reagents have their own limitations, including poor yields or diastereoselectivity, and failure to react with certain types of oxiranes.…”