Ethyloboration of Selenium Dioxide and Selenium Bis(
<i>tert</i>
‐butylimide) – Molecular Structure of an Organo‐Substituted Eight‐Membered [–BOSeO–]
<sub>2</sub>
Heterocycle
Both seleniumdioxide (1) and seleniumbis(tert-butylimide) (2) react with triethylborane (A) by 1,2-ethyloboration. In the case of 1, ethane, ethene, diethylselane (4a), tetraethyldiboroxane (Et2B)2O (B), triethylboroxine (EtBO)3 (D) and a cyclic compound [–Et2BOSe(Et)O–]2 (52) are formed after heating to 65°C. Compound 52 is also formed when 1 reacts with B. Treatment of selenous acid (3) with A
inhibited by sodium hydroxide. Acetic acid, however, removes the first ethyl group rapidly, followed by a slower removal of the second. The protonolysis of the third ethyl group requires elevated temperatures. The unusual reactivity of carboxylic acid toward protonolysis of triethylborane is attributed to the presence of both acidic and basic sites in close proximity. The effect of added reagents is also
The present invention relates to novel compounds of formula I: ##STR1## which are useful as immunomodulators, in particular, macrolide immunosuppressants. The invention also relates to the preparation of compounds of formula I, compositions containing such compounds, and methods of using such compounds.