Stereocontrol in the intramolecular Buchner reaction of diazoketones

Lipase catalyzed acylation of primary alcohols with remotely located stereogenic centres: the resolution of (±)-4,4-dimethyl-3-phenyl-1-pentanol

“…Racemic alcohols 1 and 2 were prepared via LiAlH 4 reduction of the corresponding acids 5 and 6, which were obtained as described 8 from a malonic ester reaction sequence starting from 1-phenyl-ethanol or 1-phenyl-propanol, respectively (see Scheme 1).…”

“…7 3-Alkyl-3-phenyl propanols can be oxidized into the corresponding acids or aldehydes, which are used in the synthesis of some diazoketone derivatives, which in turn have been used in Buchner cyclization reactions. 8 We have previously obtained, via lipase catalysis, pure enantiomers of b-alkyl substituted primary alcohols with good results. However, the enantioselectivity of lipase catalyzed resolutions of primary alcohols are known to be considerably lower compared to when secondary alcohols are used as substrates.…”

Lipase catalysed kinetic resolutions of 3-aryl alkanoic acids

“…108-110 C (Lit., 28 114-116 C) and with spectral characteristics identical to those described above.…”

Catalyst and substituent effects on the rhodium(II)-catalysed intramolecular Buchner reaction

“…The diazoketones 1e3 were prepared from the appropriate carboxylic acid following previously reported methodology (Scheme 2). 13,15,16 The diazoketones 1e3 were treated with rhodium(II) carboxylate or carboxamide catalysts, the most common being the standard catalyst for diazocarbonyl decompositions, Rh 2 (OAc) 4 . 17e20 McKervey has described the successful use of this catalyst for intramolecular aromatic addition, markedly improving efficiencies and yields 3,4 compared to previous reports using a series of heterogeneous copper catalysts.…”

“…4 Research from our team has previously demonstrated excellent diastereocontrol in Rh 2 (OAc) 4 -catalysed aromatic addition reactions of substrates bearing a stereogenic centre on the chain linking the diazoketone and aromatic moieties. 12,13 Herein, we report the influence of variation of catalysts and the linking chain substituents (R) on the efficiencies, regio-and stereoselectivities of the aromatic addition process. Construction of the bicyclo [5.3.0]decane systems in which the stereochemistry at the quaternary bridgehead centre is entirely controlled by internal asymmetric induction from the stereogenic centre in the side chain has considerable synthetic potential.…”