Hydrazinium dications

Alder and Sessions have reported that reductive cleavage of hydrazinium dications is a useful approach to macrobicyclic amines of the type developed by Park and Sim-mons , but the method does not appear to have been successfully applied to any cryptand syntheses. 

Hydrazinium dications and their related systems can be readily formed and show remarkable stability. These vicinal -dications show enhanced electrophilic reactivities compared to their monocationic precursors. Their chemistry has been recently reviewed,91 therefore only a brief overview is warranted here. Hydrazine itself can be doubly protonated with HC1. When... 

X-ray crystal structures have been obtained for them and the nitrogen-nitrogen distance decreases with successive oxidation. When 1,5-diazabi-cyclo[3.3.0]octane is reacted with 3-bromo-1-propanol, followed by reaction with 40% HBF4, the hydrazinium dication (197) is obtained in 80% yield (eq 51).93b The 13C labeled hydrazinium dication (198) was prepared through double alkylation of tetramethyl hydrazine, the second alkylation being assisted by the silver (I) salt (eq 52)93c... 

In the oxidation of 202, the tetracyclodiazenium ion 203 is produced in 81% yield. Like the hydrazinium dications, the diazenium dications exhibit relatively high acidities of their a-hydrogen atoms. 

Several bicyclic hydrazinium ions have been prepared and two synthetic strategies have emerged as generally useful, i.e., electrochemical oxidation and Lewis or Brpnsted acid-promoted cyclization.93 Oxidation of l,6-diazabicyclo[4.4.4]tetradecane, for example, (194) gives the intermediate radical cation (195) and the bicylic dication (196, eq 50).93a... 

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