2519-72-4Relevant academic research and scientific papers
Synthesis and characterisation of the complete series of B-N analogues of triptycene
Seven, Oemer,Popp, Sebastian,Bolte, Michael,Lerner, Hans-Wolfram,Wagner, Matthias
, p. 8241 - 8253 (2014/06/09)
The reaction between the bisborate Li2[o-C6H 4(BH3)2] and 2 equivalents of an appropriate pyrazole derivative (HpzR) in the presence of Me3SiCl yields o-phenylene-bridged pyrazaboles HB(μ-pzR) 2(μ-o-C6H4)BH (3a-3e; HpzR = 4-iodopyrazole (3a), 4-(trimethylsilyl)pyrazole (3b), 3,5-dimethylpyrazole (3c), 3,5-di(tert-butyl)pyrazole (3d), 3,5-bis(trifluoromethyl)pyrazole (3e)). The synthesis approach thus provides access to uncharged B-N triptycenes bearing (i) functionalisable groups, (ii) electron-donating or -withdrawing substituents and (iii) pyrazole rings of varying steric demand. Treatment of p-R*C 6H4BBr2 with the potassium tris(pyrazol-1-yl) borates K[HBpz3] or K[p-R*C6H4Bpz 3] yields cationic pyrazolyl-bridged pyrazaboles [p-BrC 6H4B(μ-pz)3BH]Br ([4a]Br) and [p-R*C6H4B(μ-pz)3Bp-C 6H4R*]Br (R* = Br ([4b]Br), I ([4c]Br), SiMe3 ([4d]Br)), which can be regarded as full B-N analogues of triptycene. The B-H bonds of 3b and [4a]Br are unreactive towards tBuCCH even at temperatures of 80 °C, thereby indicating an appreciable thermal stability of the corresponding B-N cage bonds. Most of the cage compounds are sufficiently inert towards water to allow quick aqueous workup. However, NMR spectroscopy in CD3OD solution reveals degradation of 3b or [4a]Br to the corresponding pyrazoles and o-C6H4(B(OCD3) 2)2 or p-BrC6H4B(OCD 3)2/B(OCD3)3. The diphenylated species [4b]Br is significantly more stable under the same measurement conditions; even after 76 d, most of the material degrades only to the stage of the syn/anti-pyrazaboles p-BrC6H4(CD3O)B(μ- pz)2B(OCD3)p-C6H4Br (11a/11b). A derivatisation of [4c]Br with nBu3SnCCtBu through Stille-type coupling reactions furnishes the alkynyl derivative [p-tBuCCC6H 4B(μ-pz)3Bp-C6H4CCtBu]Br ([4e]Br). Larger B-N aggregates are also accessible: treatment of the tetrakisborate Li4[1,2,4,5-C6H2(BH 3)4] with 4 equivalents of HpzR in the presence of Me3SiCl leads to the corresponding B-N pentiptycenes 14a-14d (HpzR = 3,5-bis(trifluoromethyl)pyrazole (14a), 4-(trimethylsilyl) pyrazole (14b), 3,5-dimethylpyrazole (14c), 3,5-di(tert-butyl)pyrazole (14d)). the Partner Organisations 2014.
FVP OF BIS- AND TRIS-(PYRAZOL-1-YL)METHANE. A RADICAL REACTION
Perez, Jorge D.,Yranzo, Gloria I.,Ferraris, Marisa A.,Claramunt, Rosa M.,Lopez, Concepcion,Elguero, Jose
, p. 6429 - 6434 (2007/10/02)
Flash vacuum pyrolysis of bis- and tris-(pyrazol-1-yl) methane was carried out.Alpha, gamma and radical eliminations were considered.The products actually formed correspond to a radical reaction.In the case of bis-(pyrazol-1-yl)methane, working at higher temperatures, pyrimidine was obtained.This compound is formed by rearrangement of a PzCH2. radical.
