96467-97-9Relevant academic research and scientific papers
The use of phosphonium anhydrides for the synthesis of 2-oxazolines, 2-thiazolines and 2-dihydrooxazine under mild conditions
Petersson, Maria J.,Jenkins, Ian D.,Loughlin, Wendy A.
experimental part, p. 739 - 746 (2009/06/20)
β-Hydroxy amides 6 and 7 were treated with triphenylphosphonium anhydride trifluoromethane sulfonate (3), or the cyclic analogue 4, to generate 2-oxazolines 5 and 8 under mild conditions. The reaction was optimised by examining the number of equivalents of reagents 3 or 4, or diisopropylethyl amine required to best effect cyclisation. The effects of altering the reaction temperature, reaction time, concentration, solvent, and addition rate also were investigated. However, it was found that use of a trityl group to block reaction at the hydroxyl or thiol group of the starting amides, and subsequent in situ detritylation, in the absence of base, led to greatly improved yields. Reagent 4 offered significant advantages in the purification of products and was used to dehydrate a range of trityl derivatives to form simple oxazolines, thiazolines, and a dihydro-1,3-oxazine, in high yield (85-99%), as well as a tetrahydro-1,3-oxazepine (31%).
Titanium(IV)-mediated tandem deprotection-cyclodehydration of protected cysteine N-amides: Biomimetic syntheses of thiazoline- and thiazole-containing heterocycles
Raman, Prakash,Razavi, Hossein,Kelly, Jeffery W.
, p. 3289 - 3292 (2007/10/03)
(matrix presented) The scope and limitations of TiCl4-mediated Δ2-thiazoline synthesis via tandem deprotection-dehydrocyclization of trityl-protected cysteine N-amides is presented. While chemical yields are acceptable (53-96%), the
