Розроблено синтетичний підхід до отримання ацил(N-метилімінодиацетил)боронатів, виходячи з 1-заміщених алкеніл-боронатів. Проведено порівняння різних методів окиснювального розщеплення ?-борильованого C-C-зв"язку. Виявлено, що процедура дигідроксилювання алкенілборонату з подальшимим розщепленням віцинального діолу є оптимальною послідов-ною. Результати показано на прикладі модельної сполуки - фенілацетил MIDA боронату. Проведено попереднє вивчення стабільності даної сполуки.
Разработан новый синтетический подход к ацил(N-метилиминодиацетил)боронатам, исходя из 1-замещённых алкенилборонатов. Проведено сравнение разных методов окислительного расщепления ?-бориллированной С-С-связи. Было обнаружено, что оптималь- ной является пошаговая процедура дигидроксиллирования алкенилбороната с последующим расщеплением вицинального диола. Результаты показаны на примере модельного соединения - фенилацетил MIDA бороната. Осуществлено предварительное изучение стабильности данного соединения.
A synthetical approach to acyl(N-methyliminodiacetyl)boronates starting from 1-substituted alkenylboronates has been developed. A comparison of different methods of oxidative cleavage of an ?-borylated C-C bound was made. It was found, that the best results can be obta&ined by sequential osmium tetroxide-catalyzed dihydroxylation of an alkene moiety followed by cleavage of the obtained vicinal diol. The cleavage procedure takes place at 0°C in homogeneous conditions (solution of periodic acid in THF) and it is comp&lete in 10 minutes (more prolonged contact with an oxidant solution results in degradation of the target compound). On the other hand, using of ruthenium tetroxide-based reagents results in overoxidation with simultaneous loss of boron moiety. Potass&ium permanganate protocols leads to the ?-borylated-?-hydroxyketone, which is prone to further oxidation. Although 1-alkyl-vinylboronates react smoothly with 3-chloroperbenzoic acid to give corresponding oxiranes (without cleavage of C-B bound), the &latter ones are stable toward action of sodium meta-periodate or periodic acid. The results were shown on the model compound - phenylacetyl MIDA boronate. Precursor of this compound, namely, Z-2-(N-methyliminodiacetylboryl)-1-phenylbut-2-ene was prep&ared in four steps, starting from common-use reagents with 32% overall yield. Thus the new approach allows acetyl MIDA boronates to be prepared just in 6 linear steps. It is remarkable, that mild and homogeneous conditions of the oxidation step permi&t to carry out this transformation on gram scale. A preliminary investigation of these substances stability towards common methods of working up and purification procedures was made. It was found, that phenylacetyl MIDA boronate and preceding diol, b&oth are stable to storage at ambient conditions (tightly closed vessel, ambient temperature) at least for one month, showing no changes in its NMR spectra. Also, these compounds are stable to extractive work up with NaHCO3, Na2S2O3 and diluted acids.& Stability toward chromatography on silica, prolonged contact with water or alcohols is limited. Structures and purity of compounds in this work was established by 1H, 13C - NMR and HPLC-analyses.
