Chemoselective allylic addition of allyltrichlorosilane to α-oxocarboxylic acids: synthesis of tertiary α-hydroxy carboxylic acids
摘要:
Allyltrichlorosilane can add to alpha-oxocarboxylic acids in the presence of DMF and HMPA. The alpha-carboxylic substituent exerts a remarkable neighboring group effect on the reaction, The reaction presumably proceeds in an intramolecular fashion through a 'rigid' bicyclic transition state assembly involving a hypervalent silicate species, which produces the chemoselectivity approaching 100%. (C) 2000 Dupont Pharmaceuticals Company. Published by Elsevier Science Ltd. All rights reserved.
A method for maintaining a total base number (TBN) above about 3 mg KOH/g for a lubricant for a diesel engine for greater than about 184 days. The method includes supplying as the lubricant, a lubricant composition comprising a sulfonate detergent having a TBN ranging from about 20 to about 100 and a phenate detergent having a TBN ranging from about 200 to about 350 and an antioxidant selected from the group consisting essentially of hindered phenolic derivatives of C
3
to C
6
acids and C
7
to C
9
esters of hindered phenolic derivatives of C
3
to C
6
acids. The phenate detergent is present in an amount that is greater than 15 percent by weight of the total weight of detergents in the lubricant composition and the lubricant composition is substantially devoid of zinc dialkydithiophosphate compounds and has a sulfated ash content of less than 1.0 wt. %.