Conformational effects in organoaluminum-promoted pinacol-type rearrangement

Conformational effects on the reaction course were examined in organoaluminum-promoted pinacol-type rearrangement, using stereo-defined unsymmetrical β-mesyloxy alcohols as the probe, where combinational use of DIBAL-Et₂AlCl achieved highly selective migration.     

Asymmetric synthesis of chiral synthons bearing alkynyl group via organoaluminum-promoted pinacol-type rearrangement

A method is described for the synthesis of chiral alkynyl ketones and alkynols via trimethylaluminum-promoted pinacol-type rearrangement where alkynyl groups behave as “the staying group”, followed by stereoselective reduction leading to the latter.     

Asymmetric synthesis of naproxen via a pinacol-type reaction

An asymmetric pinacol-type rearrangement was used in the synthesis of (S)-naproxen. The pinacol-type reaction of a vicinal diol provided an -aryl ketone which was oxidized with sodium hypochlorite in the presence of methanol to the methyl ester of naproxen.     

Reductive pinacol-type rearrangement of chiral α-mesyloxy ketones promoted by organoaluminum compounds

Reductive pinacol-type rearrangement of chiral α-mesyloxy ketones was effected by organoaluminums (DIBAL in combination with Et₃Al or Et₂AlCl) leading to enantiomerically pure 2-aryl- or 2-alkenyl-1-propanols.     

Structure and Reactivity of Xanthocorrinoids. Part III. The first example of a pinacol-type rearrangement in the corrin series

The transformation of the c-acetic-acid chain of hexamethyl Coα, Coβ-dicyanocobyrinate into an ethyl group (→ 2 ) as well as the synthesis of the pentadecaalkyl-cobalticorrin 6d from commercial cyanocobalamin are described. On reaction of 2 or 6d with O₂ in the presence of ascorbic acid, migration of the CH₃ group at C(5) to the vicinal position C(6) takes place concomitantly with the introduction of a carbonyl group at C(5).     

Completely stereospecific 1,2-migration of alkyl groups in Et2AlCl promoted pinacol-type rearrangement

Completely stereospecific 1,2-migration of alkyl groups was achieved in Et₂AlCl promoted pinacol-type rearrangement of chiral β-mesyloxy alcohols to give optically pure α-alkyl ketones including both enantiomers of 4-methyl-3-hexanone, an alarm pheromone of ant.     

Steroids I. Alkylation of β-ketoesters via their Cu(II) enolates in aqueous media. Application of the synthesis of C-18 functionalized steroids via the torgov approach.

Three steroidal pentaenes ($\underset{?}{8}$a?$\underset{?}{\mathrm{c}}$) have been synthesized, the key step being the alkylation of the Cu(II) chelates to the ring D precursors ($\underset{?}{3}$?$\underset{?}{5}$) by the isothiouronium acetate $\underset{?}{1}$ in aqueous solution.     

Stable selenoketenes via selena-cope rearrangement

Selena-Cope rearrangement of selenides $\text{4c,d}$ leads to allyl(silyl)selenoketenes $\text{5c,d}$, which could be fully characterised spectroscopically as well as by typical addition and cycloaddition reactions.     

A homologous ester claisen rearrangement via the cope rearrangement of O-trimethylsilylcyanohydrins

The Cope rearrangement of 1,5-dienyl trimethylsilyl-cyanohydrins to α-trimethylsilyoxy-α,β-unsaturated nitriles and their cleavage to methyl δ-hexenoates is discussed.     

O-Arylsulfonyl hydroxylamines via a decarboxylative rearrangement

(E)-O-Arylsulfonyl-N-(2-nitroalk-2-enyl)hydroxylamines were easily obtained in good yields starting from (E)-nitro allylic alcohols, the crucial step being an inorganic base-catalyzed decarboxylative rearrangement of proposed labile unsaturated carbamates. A possible mechanism for the outcome of the reaction, characterized by the unusual retention of the sulfonyloxy group, is proposed.