N,O-Bis(trimethylsilyl)hydroxylamine

Clear colorless liquid

bp 137–139°C, 78–80°C/100 mmHg; d 0.830 g cm3; flash point 28°C.

N,O-Bis(trimethylsilyl)hydroxylamine has been used as reagent for the preparation of N-(dialkyl phosphinoyl)hydroxylamines and migration of simple alkyl groups in rearrangement of their O-p-nitrobenzenesulfonates.

N,O-Bis(trimethylsilyl)hydroxylamine is a protected, lipophilic form of hydroxylamine. It reacts with a variety of electrophiles predominantly by attack on the nitrogen nucleophilic center. Reaction with acid chlorides (1 equiv) in the presence of triethylamine gives N,O-bis(trimethylsilyl)- hydroxamic acids by N-acylation.A related reagent, tris(trimethylsilyl) hydroxylamine, gives the same product in high yields, also by N-acylation.Hydrolysis gives the free hydroxamic acids, whereas thermal fragmentation affords isocyanates (eq 1).

N,O-Bis(trimethylsilyl)hydroxylamine can be prepared in 69% yield by treating dry hydroxylamine with equiv chlorotrimethylsilane and equiv triethylamine.A safer preparation, which avoids the use of the explosive solid, hydroxylamine, uses the reaction of hydroxylamine hydrochloride with excess hexamethyldisilazane (71–75% yield).Alternatively, neutralization of hydroxylamine hydrochloride with ethylenediamine followed by addition of chlorotrimethylsilane can be used.

N,O-Bis(trimethylsilyl)hydroxylamine on reaction with 9-chloro-9-borafluorene yields 10-trimethylsilyloxy-9-aza-10-boraphenanthrene. It reacts with free phenolic steroids during the analysis of conjugated estrogen tablets and injectable formulations by GLC.