L-Alkene-4-ols

Ti-BINOL-catalyzed reactions have been well established. When the Ti is replaced by Zr,92 the resulting complex 140 can also catalyze the addition of allyl-tributyltin to aldehydes (aldehydes allyl-tributyltin 140 = 1 2 0.2 mol ratio) in the presence of 4 A MS. Product l-alken-4-ols are obtained in good yield and high ee. The, Sz-face of the aldehyde is attacked if (S)-BINOL is used, and Re-face attack takes place when (K)-BINOL is used as the chiral ligand. For Zr complex-catalyzed reactions, the reaction proceeds much faster, although the... 

Oxidation of l-alkene-4-ols. These substrates are oxidized by PdCl2 (catalytic) and p-benzoquinone (3 equiv.) or by CuCl/O, at 40° to y-butyrolactols (cyclic hemiacetals), precursors to y-butyrolactones.1... 

B-MethaHyldiisopinocampheylborane (4). This reagent (4), prepared by reaction of (+ )-B-methoxydiisopinocampheylborane with mediallyllithium, reacts with aldehydes to give, after oxidation, 2-methyl-l-alkene-4-ols (5) with >90% ee. 

Hetero allylboranesP The 3-amino- and 3-silylallyl derivatives are very valuable reagents for the synthesis of anti-3-amino-l-alken-4-ols and anfi -l-alkene-3,4-diols, respectively, by condensation with aldehydes. In the latter cases, an oxidative desilylation is required. 

Allylzirconocene chlorides. These re l-alken-4-ols by reaction with aldehydes h derived from allenylstannanes condense i... 

Allylzirconocene chlorides. These reagents are formed from allenes. A route to l-alken-4-ols by reaction with aldehydes has been developed. 1,1-Bimetallic species derived from allenylstannanes condense with aldehydes to form 1,3-dienes. ... 

The catalyst formed by reaction of these polymer-bound ligands 4 a and 5 with [Rh(nbd)2]S03CH3 (nbd = norbornadiene) was used for hydrogenation of water-soluble (and also water-insoluble) alkenes in aqueous solution. The hydrogenation of acrylic acid proceeded smoothly (TOF ca. 100 h 1 at 25 °C, 1 atm) in water with the PEI-bound catalyst, whereas with the PAA-bound catalyst precipitation of the catalyst occurred due to the change in pH caused by the added acrylic acid [10c], A possible effect of salt formation of acrylic acid with the basic PEI on the reactivity of the unsaturated acid was not investigated. With l-buten-4-ol as the substrate... 

Highly enantioenriched 4-alken-l-yn-3-ol moieties present in many bioactive acetylenic metabolites from sponges have been efficiently obtained by reduction of the parent 1-trimethylsilyI-4-alken-l-yn-3-one 18 with Alpine-borane or with BH3-SMe2 in the presence of chiral oxazaborolidines, followed by desilylation of the resulting alcohol. This strategy has been applied to the first stereoselective synthesis of petrofuran 19 <99SL429>. 

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