p,p'-Dinitrobenzhydryl ethers, acid and base stable protecting groups, which are readily removable in the presence of benzyl and monomethoxytrityl functions

Abstract

4-(Benzyloxy)-2-fluoro-2-methylbutan-l-ol (3f): 0.69 g (31%); Rf 0.15 (hexanes/ethyl acetate, 3:1);

Post‐Polymerization Modification of Materials using Diaryldiazomethanes: Changes to Surface Macroscopic Properties

“…Carbenes, on the other hand, are reported to insert with high efficiency into O–H and C–H bonds but we found in preliminary investigations that diaryldiazomethanes do not necessarily exhibit high reactivity in solution despite their reported reactivity with carboxylic acids, alcohols, amines, and alkenes, amongst other functional groups . We wondered if the incorporation of electronically modifying groups might give an acceptable balance of stability and reactivity, favouring insertion into low surface energy polymers, and preliminary work with methoxy‐activated systems 1 (R = OMe) indicated that although polymer modification was possible, even more reactive systems would be desirable.…”

5‐endo‐dig Cyclization of O‐Propargyl Mandelic Acid Amides towards 2,5‐Dihydrofurans

“…Thus, we decided to examine the behavior of alternative starting materials replacing secondary amides by tertiary amides or esters. Due to poorly efficient O‐propargylation of ethyl mandelate under our conditions, we decided to prepare O‐propargyl ester 6 using a BF 3 triggered reaction of diazoester 5 as reported by Just et al (Scheme ) . When 6 was treated under our optimized cyclization conditions, the expected 2,5‐dihydrofuran 7 was not formed but we could isolate out of the complex mixture the 2,5‐dihydrofuran 8 obtained in a low 12 % yield (Scheme ).…”

Nucleotides, Part LXVIII, Acetals as New 2′-O-Protecting Functions for the Synthesis of Oligoribonucleotides: Synthesis of Monomeric Building Units and Oligoribonucleotides

“…It will be an exciting challenge for the future to synthesize longer RNA fragments of high quality using these new protected protecting groups, approach and the corresponding easy workup procedures. 2 (14). According to 2.1, from 2 with 6.…”

“…There are practical solutions of the problem leading to longer RNA sequences [2 ± 6] since, for 2'-OH protection, the tbds ((tert-butyl)dimethylsilyl group) [7 ± 9] or the fpmp (1-(2-fluorophenyl)-4-methoxypiperidin-4-yl) [6] [10] residue can be used. Still, some side reactions [10] [11] have to be overcome, especially when other blocking groups such as the 2-nitrobenzyl (nbn) [12], the dianisoyltrichloroethyl (date) [13], the 4,4'-dinitrobenzhydryl (dnbh) [14], the [2-(4-nitrophenyl)ethyl]sulfonyl (npes) [15], or the acetal functions tetrahydro-2H-pyran-2-yl (thp) [16], tetrahydro-4-methoxy-2H-pyran-2-yl (mthp) [17], [(trimethylsilyl)ethoxy]ethyl (see) [18], 3-methoxy-1,5-bis(methoxycarbonyl)pentan-3-yl (mdmp) [19 ± 21], 1-alkoxyethyl-and 1-(2-chloroethoxy)ethyl (cee) [22] are applied.…”