‘Click’ Chemistry on Sugar-Derived Alkynes: A Tandem ‘Click-Click’ Approach to Bistriazoles

Abstract

Development of a tandem 'click-click' approach to the formation of successive 1,4-disubstituted 1,2,3-triazole linkages and 'click chemistry' on sugar-derived alkynes are described.

Regioselective azidotrimethylsilylation of carbohydrates and applications thereof

“…This observation was substantiated by reacting methyl-3-O-benzyl-α-Dxylopyranoside (22) with TMSN 3 under standardised reaction conditions. The formation of persilylated product 22a ( Table 3, entry 7) was in accordance to the proposed explanation on the 20 basis of the reactivity of hydroxyl groups. Further, as expected the reaction of diacetonide galactopyranoside 23 ( Table 3, Table 3, entry 9) also afforded the corresponding azido compound 23a (67%) and silylated compound 24a (85%) respectively.…”

“…The formation of 1a can be easily explained by 15 conventional reaction pathway through the formation of silyloxyphosphonium ion intermediate followed by nucleophilic attack by azide ion at less hindered terminal carbon (Fig. 1 20 In order to obtain 1a as the sole product, the substitution of DIAD with DEAD or DBAD under varied reaction conditions (Table 1) did not make any difference in the pattern of product formation. However, using DIAD as oxidiser and toluene as a solvent (Table 1, entries 7) at lower temperature (0 °C), there was a marked 25 change in the product distribution and 1a was obtained almost as an exclusive product.…”

“…3 They act as precursors of highly reactive intermediates such as nitrenes and nitrenium ions, as well as more common and ubiquitous functional groups such as amines, aziridines, triazoles etc. 1 Although, among the most reactive 20 functional groups, azides are often completely inert, at least from a kinetic point of view. In this context, carbohydrates bearing azido functions have emerged as attractive intermediates, bringing forth the 'click' adducts with their intrinsic properties (polarity, solubility, biocompatibility, biodegradability including 25 biological role etc.)…”

“…The yellow reaction mixture was stirred at this temperature for 30 minutes under nitrogen followed by the addition of Me 3 SiN 3 (1.3 mmol, 155 µL). The reaction mixture was further stirred at the same temperature for 3 h before allowed to warm to room 20 temperature. The completion of the reaction was monitored by TLC.…”

“…IR (CHCl 3 ): 3034, 2927.96, 2101.02, 1254.20, 1154.56, 1032.62, 844, 734cm -1 . [α]20 Hz, 1H), 4.16 (s, 1H), 4.04 (m, 1H), 3.87 (d, J = 4.6 Hz, 1H), 3.71 (dd, J = 2.4, 13.1 Hz, 1H, H-6a/b), 3.43 (dd, J = 4.6, 13.1Hz, 1H, H-6a/b), 3.38 (s, 3H, -OCH 3 ), 0.09 (s, 9H). 13 C NMR (125 MHz, CDCl 3 ) δ; 138.1, 137.8, 128.5, 128.4, 128.3, 128.2, 128.1, 128.0, 127.9, 127.86, 127.84, 127.7, 110.8, 83.0, 80.4, 78.5, 76.allofuranoside (20a).…”