Direct Regioselective C-H Cyanation of Purines

Abstract

A direct regioselective C-H cyanation of purines was developed through a sequential triflic anhydride activation, nucleophilic cyanation with TMSCN, followed by a process of base-mediated elimination of triflous acid (CF3SO2H). In most cases, the direct C-H cyanation occurred on the electron-rich imidazole motif of purines, affording 8-cyanated purine derivatives in moderate to excellent yields. Various functional groups, including allyl, alkynyl, ketone, ester, nitro et al. were tolerated and acted as a C8 directing group. The electron-donating 6-diethylamino, as C2-directing group substituent, can switch the regioselectivity of purine from 8- to 2-position, enabling the synthesis of 8- and 2-cyano 6-dialkylaminopurines from corresponding 6-chloropurine in different reaction order. Further functional manipulations of the cyano group allow the conversions of 8-cyanopurines to corresponding purine amides, imidates, imidothioates, imidamides, oxazolines, and isothiazoles.

Waste Glass in Road Construction: A Review

“…Ground Waste glass Source: [24] Fig. 4.Glass Powder Source: [24] According to Li et al [25], adhesion loss is a primary problem of asphalt caused by water especially in the case of asphalt mixture which contains waste glass powder. This problem is associated with the smoothness of the glass surface which affect the adhesion of the bitumen aggregate and eventual acceleration of stripping.…”

Understanding the active sites and associated reaction pathways of metal-free carbocatalysts in persulfate activation and pollutant degradation

“…The increasing environmental pollution with the fast development of various industries calls for efficient and lowcost methods to remove the toxic and refractory pollutants from water radically. [1][2][3][4] The current methods involve adsorption, [5][6][7] Fenton oxidation, 8,9 Fenton-like oxidation, 10,11 electro-Fenton, 12,13 photo-Fenton, 14,15 electrochemical oxidation, 16,17 photocatalysis [18][19][20][21] and others. [22][23][24][25][26] Among these methods, Fenton-like oxidation based on peroxomonosulfate (PMS) and peroxydisulfate (PDS) has attracted significant attention due to its long life spans, strong oxidation ability, ease of storing and transporting PMS/PDS relative to liquid H 2 O 2 , applicability to a diversity of refractory organic pollutants, and capability to withstand a wide pH range, which is superior to the Fenton process requiring H 2 O 2 as the reactant, thus causing the storage and delivery to be difficult.…”