90269-18-4

Upstream product

• 16837-06-2 p-(3,3,4,4-tetramethyl-2,5-dioxa-1-borolyl)nitrobenzene 
• 90269-20-8 4,4,5,5-Tetramethyl-2-(4-nitro-phenyl)-[1,3]dioxolan-2-ol 

Downstream Products

• 90269-20-8 4,4,5,5-Tetramethyl-2-(4-nitro-phenyl)-[1,3]dioxolan-2-ol 
• 90269-19-5 4,4,5,5-Tetramethyl-2-(4-nitro-phenyl)-[1,3]dioxolan-2-ol anion 

Relevant academic research and scientific papers

Observation of a Stable Hemiortho Ester Anion. Acidity Constant for a Tetrahedral Intermediate

Pinacol mono-p-nitrobenzoate (POH) undergoes a rapid, reversible cyclization in base producing an anionic tetrahedral intermediate (TO-), the conjugate base of 2-(p-nitrophenyl)-2-hydroxy-4,4,5,4-tetramethyl-1,3-dioxolane (TOH).Presence of the anion is established by changes in UV spectra and by the rate behavior exhibited in the hydrolysis of the ester to pinacol and p-nitrobenzoate.Rate constants in base do not rise as rapidly as expected as the ester form is converted to the unreactive TO-.Interconversion of POH and TO- occurs in a typical acid:base manner, and UV spectral analysis in base provides Kb= ->/->=0.7.The equilibrium constant K0=/ for cyclization of the pinacol ester to the neutral hemiortho ester TOH is 8*10-4, this has been measured as the ratio of forward and reverse rate constants.Combination of Kb and K0 provides a value Ka=->+>/ for the acidity constant of the tetrahedral intermediate of 10-10.4.This number is compared with estimates of tetrahedral intermediate acidity based on substituent effects and free energy correlations, and excellent agreement is noted.

Reactions of 1,3-dioxolanes with Iodine Monochloride: Formation of Chlorohydrin Esters and Diol Monoesters

2-Mono-substituted 1,3-dioxolanes are oxidised by iodine monochloride to the appropriate 2-substituted 1,3-dioxolan-2-ylium ions, whose stability is dependent upon the presence and nature of substituents on C-4 and C-5.Some dioxolanylium ions are labile and under the reaction conditions afford chlorohydrin esters, with inversion of configuration taking place at the ring carbon attacked by chloride.Others are stable under the reaction conditions and may be converted on aqueous workup to diol monoesters with retention of configuration at C-4 and C-5.The effect of substituents and reaction conditions on these competing reactions are described.The stereo- and regio-chemistry of both hydroxy- and chloro-ester formation was confirmed through NMR studies, which necessitated the prior detailed analysis of the 1H and 13C spectra associated with the acyloxy sidechains of the relevant esters.