Metalated Azolo[1,2,4]triazines. I. Synthesis of 2‐(6‐tert‐Butyl‐5‐oxo‐4,5‐dihydro‐1,2,4‐triazin‐3(2H)‐ylidene)acetonitriles via Ring Opening Degradation of 3‐tert‐Butyl‐7‐lithio‐4‐oxo‐4H‐pyrazolo[5,1‐c][1,2,4]triazin‐1‐ides

Abstract

1,7,8‐Polymetalated 3‐tert‐butyl‐8‐R‐4‐oxo‐4H‐pyrazolo[5,1‐c][1,2,4]triazines (M = Li, Na; R = CO2Et, CN, H, D, and Li) have been generated for the first time using acidic NH deprotonation and lithium/bromine exchange method at −112 ÷ −97°C. The rapid pyrazole ring opening degradation of the unstable 7‐lithio‐4‐oxopyrazolo[5,1‐c][1,2,4]triazines at −97°C led to formation of 2‐(6‐tert‐butyl‐5‐oxo‐4,5‐dihydro‐1,2,4‐triazin‐3(2H)‐ylidene)acetonitriles. Furthermore, lithium, sodium ((6‐tert‐butyl‐5‐oxo‐5H‐1,2,4‐triazin‐2,4‐diid‐3‐ylidene)(cyano)methyl)lithium was successfully generated from 7,8‐dibromo‐3‐tert‐butylpyrazolo[5,1‐c][1,2,4]triazin‐4(6H)‐one, sodium hydride, and tert‐butyl lithium, and an electrophile trapping using H2O, dimethylformamide, t‐BuCOCl, and PhCOCl allowed the selective side‐chain functionalization. Structures of the isolated products have been established on the basis of IR, 1H, 2H, 13C NMR, and high‐resolution mass spectra.

Synthesis and DFT analysis of non-covalent interactions in crystal structures of 6-R-2-alkoxy-, 2,3-di-, and 2,2,3-tri-tert-butylpyrrolo[1,2-b][1,2,4]triazines

“…All operations, except for chromatography, were carried out in argon atmosphere. Starting compound 1 was synthesized as described in literature [18].…”

Synthesis and crystal structures of 7,8-bromo (dibromo)-3-tert-butylpyrazolo[5,1-c][1,2,4]triazines

“…All reagents were obtained from commercial sources and used without additional purification. Starting compounds 1a,b, 2a-d, and 3a were synthesized as described in literature (Scheme 1) [17][18][19][20].…”

“…The starting compounds 1a,b were prepared by cyclocondensation of 4-amino-6-tert-butyl-3-methylsulfanyl-1,2,4-triazin-5-one with cyanoacetic acid derivatives in pyridine (Scheme 1) [18]. Hydrolysis of the pyrazole ester moiety in 1a and diazotization using tert-butyl nitrite gave 7-unsubstituted acid, which is converted to compound 2a by halodecarboxylation [17].…”

“…Hydrolysis of the pyrazole ester moiety in 1a and diazotization using tert-butyl nitrite gave 7-unsubstituted acid, which is converted to compound 2a by halodecarboxylation [17]. Alternatively, treatment of 1a,b with trimethylsilylbromide/t-BuONO followed by bromination or selective reduction of the CO 2 Et group with diborane led to compounds 2b or 2d, respectively [18,19]. Compound 2c [18] was prepared by a selective C(8)-site Li/Br exchange in 2b using n-butyl lithium at low temperature, and further protonation.…”

“…Nevertheless, the structural features of such systems are still relatively poorly studied. In continuation of our studies on the chemical and structural properties of functionalized pyrazolo [5,1-c] [1,2,4]triazines [16][17][18][19][20][21], in the present work, we discuss the single crystal structures in a series of brominated 4-oxo-and novel 4unsubstituted-3-tert-butylpyrazolo [5,1-c] [1,2,4]triazines, including bond lengths and angles, non-valence interactions, and packing modes.…”