3-Alkoxycarbonyl-3-hydroxy-substituted

Stereochemical outcome of this rearrangement. Enolization of the regioisomeric esters (127) and (128) has been shown to afford a-allyloxy-substituted ester dienolates (129) which undergo a [2,3]-sigmatropic rearrangement to yield 3-alkoxycarbonyl-3-hydroxy-substituted hexa-1,5-dienes (130). These have been transformed to diastereomerically pure 2,3-dialkenyl-substituted (/-lactones (131). 

The Pd(II)-catalysed cycloisomerization of 3-alkoxycarbonyl-3-hydroxy-substituted 1,5-hexadienes has been studied experimentally and computationally and two productforming catalytic cycles are proposed. A review of transition-metal-catalysed cycloi-somerizations of a, -dienes has been published (Scheme 141). ... 

In each table, substituted azoles are ordered in the following way alkyl, substituted alkyl, aryl, formyl, acetyl, carboxylic acid, alkoxycarbonyl, cyano, amino, azido, diazonium salt, nitroso, nitro, hydroxy, alkoxy, fluoro, chloro, bromo, and iodo. 

The esters of aliphatic a- and /J-hydroxy carboxylic acids react with sulfur tetrafluoride to form mixtures of the corresponding esters of fluorocarboxylic acids and alkoxycarbonyl fluoro-sulfites. If there are electron-withdrawing substituents, such as trifluoromethyl groups, in the a-position the carbonyl oxygen is substituted by two fluorine atoms without substitution of the hydroxy group. ... 

FITS reagents reacted very easily with thiols in the presence of pyridine to give the perfluoroalkyl sulfides in good to high yields. S-perfluoroalkylation was selective in the case of polyfiinctional substrates. In the presence of groups such as hydroxy, carboxy, alkoxycarbonyl or dialkylamino, the sulfur atom was always selectively substituted.216 (Table 5.10)... 

Kennedy and Hall have reported a one-pot allylboration/lactonization using the tetra-substituted 2-alkoxycarbonyl aUylboronates 17 (Section 6.2.1.2) [39]. These allyl-boronates react with aldehydes, thermally and under Lewis acid catalysis, to first provide the hydroxy-ester intermediate 119 (Equation 58). This initial product cyclizes under the reaction conditions by lactonization to afford a-exomethylene y-lactones 120. This facile cyclization is probably a manifestation of the gem-dialkyl effect. In-... 

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