78388-16-6Relevant articles and documents
Mild, Rapid, and Chemoselective Procedure for the Introduction of the 9-Phenyl-9-fluorenyl Protecting Group into Amines, Acids, Alcohols, Sulfonamides, Amides, and Thiols
Soley, Jacob,Taylor, Scott D.
, (2020/02/04)
The 9-phenyl-9-fluorenyl (PhF) group has been used as an Nα protecting group of amino acids and their derivatives mainly as a result of its ability to prevent racemization. However, installing this group using the standard protocol, which employs 9-bromo-9-phenylfluorene/K3PO4/Pb(NO3)2, often takes days and yields can be variable. Here, we demonstrate that the PhF group can be introduced into the amino group of Weinreb's amides and methyl esters of amino acids, as well as into alcohols and carboxylic acids, rapidly and in excellent yields, using 9-chloro-9-phenylfluorene (PhFCl)/N-methylmorpholine (NMM)/AgNO3. Nα-PhF-protected amino acids can be prepared from unprotected α-amino acids, rapidly and often in near quantitative yields, by treatment with N,O-bis(trimethylsilyl)acetamide (BSA) and then PhFCl/NMM/AgNO3. Primary alcohols can be protected with the PhF group in the presence of secondary alcohols in moderate yield. Using PhFCl/AgNO3, a primary alcohol can be protected in good yield in the presence of a primary ammonium salt or a carboxylic acid. Primary sulfonamides and amides can be protected in moderate to good yields using phenylfluorenyl alcohol (PhFOH)/BF3·OEt2/K3PO4, while thiols can be protected in good to excellent yield using PhFOH/BF3·OEt2 even in the presence of a carboxylic acid or primary ammonium group.
REACTIONS OF N-SULFINYL-p-TOLUENESULFONAMIDE WITH ALCOHOLS
McFarland, John W.,Schut, Dirk,Zwanenburg, Binne
, p. 389 - 393 (2007/10/02)
N-Sulfinyl-p-toluenesulfonamide (1) reacted with triaryl- and diarylmethanols to give predominantly N-substituted sulfonamides and SO2 presumably via carbonium ion intermediates.When carbonium ion forming alcohols, such as t-BuOH and Ph2C(Me)OH, were used, the predominant products were alkenes and p-toluenesulfonamide.Allylic alcohols afforded N-substituted sulfonamides, along with dienes and p-toluenesulfonamide.Alcohols wich could not predictably give relatively stable intermediate carbonium ions, gave either dialkyl sulfites or dialkyl ethers, along with p-toluenesulfonamide.In one case, namely with 9-phenylfluorenol, the 1:1 adduct with 1 (an amidosulfite) was isolated.A mechanism for the reaction is proposed.
