32228-19-6Relevant academic research and scientific papers
Electrophilic Vinylation of Thiols under Mild and Transition Metal-Free Conditions
Castoldi, Laura,Di Tommaso, Ester Maria,Gr?fen, Barbara,Olofsson, Berit,Reitti, Marcus
supporting information, p. 15512 - 15516 (2020/06/23)
The iodine(III) reagents vinylbenziodoxolones (VBX) were employed to vinylate a series of aliphatic and aromatic thiols, providing E-alkenyl sulfides with complete chemo- and regioselectivity, as well as excellent stereoselectivity. The methodology displays high functional group tolerance and proceeds under mild and transition metal-free conditions without the need for excess substrate or reagents. Mercaptothiazoles could be vinylated under modified conditions, resulting in opposite stereoselectivity compared to previous reactions with vinyliodonium salts. Novel VBX reagents with substituted benziodoxolone cores were prepared, and improved reactivity was discovered with a dimethyl-substituted core.
Tuning the stereoelectronic properties of 1-sulfanylhex-1-enitols for the sequential stereoselective synthesis of 2-deoxy-2-iodo-β- d -allopyranosides
K?vér, Andrea,Boutureira, Omar,Matheu, M. Isabel,Díaz, Yolanda,Castillón, Sergio
, p. 3060 - 3068 (2014/05/06)
The preparation of challenging 2-deoxy-2-iodo-β-d-allo precursors of 2-deoxy-β-d-ribo-hexopyranosyl units and other analogues is reported using a robust olefination-cyclization-glycosylation sequence. Here, we particularly focus on tuning the stereoelectronic properties of the alkenyl sulfides intermediates in order to improve the diastereoselectivity of the cyclization step and, hence, the efficiency of the overall transformation. Phosphine oxides with the general formula Ph2P(O)CH2SR (R = t-Bu, Cy, p-MeOPh, 2,6-di-ClPh, and 2,6-di-MePh) were easily synthesized and subsequently used in the olefination reaction with 2,3,5-tri-O-benzyl-d-ribose and -d-arabinose. The corresponding sugar-derived alkenyl sulfides were submitted to a 6-endo [I+]-induced cyclization, and the resulting 2-deoxy-2-iodohexopyranosyl-1-thioglycosides were used as glycosyl donors for the stereoselective synthesis of 2-deoxy-2-iodohexopyranosyl glycosides. Among the different S-groups studied, t-Bu derivative was the best performer for the synthesis of cholesteryl 2-deoxy-2-iodomannopyranosides, whereas for the synthesis of 2-deoxy-2-iodoallopyranosides none of the derivatives here studied proved superior to the phenyl analogue previously described. Glycosylation of cholesterol with different d-allo and d-manno derivatives produced 2-deoxy-2-iodoglycosides with stereoselectivities in the same order in each case, reinforcing the involvement of an oxocarbenium ion as the common intermediate of this crucial glycosylation step.
