Oxygen nitrogen exchange

Treatment of the previously mentioned 3-(2-uIso-l-yl)indoles 41 (Section II,C,2) with acetic anhydride and perchloric acid gave the indole[2,3-c]pyrylium perchlorates 65. Ammonium hydroxide in ether caused oxygen-nitrogen exchange and provided 66 [68DOK849, 68MI3] (Scheme 21). 

The oxygen-nitrogen exchange in titanates is achieved via an ammonolysis reaction [132] ... 

After being precooled with product oxygen in exchanger E-l and with product nitrogen in E-2, the air serves as the heating medium in reboiler E-3 of column T-2. Its pressure then is reduced to 100 psig, and it is fed to the middle of column T-2. Bottoms of T-2 is fed to the middle of column T-3. This stream contains 40% oxygen. 

PROTONS ON OXYGEN, NITROGEN, AND SULFUR ATOMS. EXCHANGEABLE PROTONS... 

Most importantly, the scope of the Diels-Alder reaction is very high - not only allowing the synthesis of cyclohexenes and 1,4-cyclohexadienes using 1,3-butadienes and alkenes and alkynes, respectively, but also giving access to a multitude of different heterocycles by exchanging the atoms a-d in the butadiene as well as the atoms e and f in the alkene by hetero atoms such as oxygen, nitrogen and sulfur. However, also dienes and dienophiles with several other atoms as phosphorous, boron, silicone, and selenium have been described. Thus, many different heterodienes and heterodienophiles have been developed over the years (Tables 1-1 and 1-2). 

Anew synthetic method involves reaction with an A -substituted iminophosphorane, which is accompanied by oxygen-nitrogen heteroatom exchange (Eq. 182). ... 

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