28248-35-3Relevant academic research and scientific papers
Unexpected alkoxyl migration in the reaction of silyl ketene acetals with p-toluenesulfonyl azide
Xu, Yong,Zhu, Shizheng
, p. 3909 - 3913 (2001)
The reaction of p-toluenesulfonyl azides with several silyl ketene acetals has been investigated. 1-Trimethylsilyloxy-ethylene reacted with TsN3 to give a good yield of N-p-toluenesulfonyl substituted glycinates exclusively. However, during the reaction of 1-trimethylsilyloxy-propene with TsN3, an unexpected alkoxyl migration occurred to give N-acylsulfonyl amides; other products, N-p-toluenesulfonyl substituted aziridines were also obtained. In the case of dialkyl substituted silyl ketene acetals, three products were formed, i.e. aziridines, α-amino esters, and N-acylsulfonyl amides. The mechanism for the alkoxyl migration was discussed.
Stereoselective synthesis of 2,4,5-trisubstituted piperidines by carbonyl ene and Prins cyclisations
Cariou, Claire A.M.,Kariuki, Benson M.,Snaith, John S.
supporting information; experimental part, p. 3337 - 3348 (2009/02/05)
An approach to 2,4,5-trisubstituted piperidines is reported, in which the key step is the Prins or carbonyl ene cyclisation of aldehydes of the type 1. Prins cyclisation catalysed by concentrated hydrochloric acid in CH 2Cl2 at -78 °C afforded good yields of two of the four possible diastereomeric piperidines, with the 4,5-cis product 7 predominating in a diastereomeric ratio of up to 94: 6. The diastereoselectivity of the cyclisation decreased as the 2-substituent increased in size, becoming unselective for very bulky 2-substituents. In contrast, cyclisation catalysed by MeAlCl2 in CH2Cl2 or CHCl3 at temperatures of between 20-60 °C, favoured the 4,5-trans diastereomer 8, in a diastereomeric ratio of up to 99: 1. The low-temperature cyclisations catalysed by HCl proceed under kinetic control via a mechanism involving the development of significant carbocationic character, in which the 4,5-cis cation is more stable than the 4,5-trans cation as a result of overlap with the neighbouring oxygen. The cyclisations catalysed by MeAlCl2 proceed under thermodynamic control, affording the product in which both the 4- and 5-substituents are equatorial.
SYNTHESIS OF SOME I-AMINO ALICYCLIC CARBOXYLIC ACIDS AND THEIR DERIVATIVES
CREMLYN RJW,ELLAM RM,MITRA TK
, p. 218 - 220 (2007/10/08)
A number of isomeric 1-amino alicyclic carboxylic acids have been prepared via the Bucherer and Strecker routes. These amino acids have been converted into the corresponding copper complexes; p- toluenesulphonyl derivatives of the methyl esters of the amino acids have also been prepared. It is observed that the p- toluenesulphonyl derivatives of the methyl esters of Bucherer amino acids are generally obtained in higher yields as compared with the derivatives of Strecker amino acids, under identical experimental conditions.
