Azidohydrins

The azidohydrins obtained by azide ion opening of epoxides, except for those possessing a tertiary hydroxy group, can be readily converted to azido mesylates on treatment with pyridine/methanesulfonyl chloride. Reduction and subsequent aziridine formation results upon reaction with hydrazine/ Raney nickel, lithium aluminum hydride, or sodium borohydride/cobalt(II)... 

An example of ring enlargement is the intramolecular Schmidt reaction of azidoalkyl ketone 53 that gives, by the action of titanium tetrachloride, through intermediate azidohydrin, lactam 20 (95JA10449). Because of the large distance between keto and azido groups, the usual catalyst trifluoroacetic acid does not work. 

A further advantage of this protocol is that it allows the azidohydrin intermediate to be isolated. This will facilitate important mechanistic work to clarify the nature of the reactive species responsible for the ring expansion. Although only the preparation of azepin-2-... 

Azidohydrin. See individual azido derivatives of the hydrogen acid ester of a polyatomic alcohol, such as glycol glycerol, etc... 

N3)2Ti(0-i-Pr)2 (l) 10 azidohydrins. Azidotrimethylsilane reacts very slowly in the presence of Ti(0-/-Pr)4 with epoxides to form azidohydrins. The reaction is more rapid when catalyzed by 1. Actually 1 is a superior reagent for cleavage of 2,3-epoxy alcohols.11 Examples ... 

A novel approach to the synthesis of lactams has been reported56 which involves reaction of such enol ethers with TMS-azide to give (triisopropylsilyl)azidohydrins, which then undergo a photoinduced Schmidt rearrangement (equation 14). 

The reaction with a ketone gives an azidohydrin intermediate, which rearranges to form an amide ... 

Trimethylsiloxy azides. This system reacts rapidly with epoxides to give trimethylsiloxy azides by attack at the less-substituted carbon. The products are precursors to azidohydrins and (3-amino alcohols. 

Azidohydrins. Epoxides are converted to trans-siloxy azides by reaction with N3Si(CH3)3 (1.5 equiv.) and aluminum isopropoxide (1 equiv.) in CH2C12. The reaction involves selective attack of azide on the less-substituted carbon of the epoxide. 

Side reactions at the azidohydrin stage 5 have not been unequivocally identified but the subsequently formed iminodiazonium ion 6 can fragment to nitriles and species derived from a carbonium ion , reaction (34), and such a mode of reacdon accounts for most of the... 

It is apparent, then, that precursors for terminal vinyl azides are obtained following iodine azide addition to olefins only when rather unusual steric or electronic factors are operating. A number of other reaction sequences have been investigated in the search for a general approach to the terminal compounds. The opening of a terminal epoxide by azide ion leads to an azidohydrin which can be readily dehydrated (equation 4). Unfortunately, this reaction sequence... 

The preparation of 22 was accomplished by a sequence involving the sodium borohydride reduction of phenacyl azide, followed by the conversion of the resulting azidohydrin to the azidochloride, which was then subjected to base-catalysed elimination (equation 5). 

Alkali metal azides react with epoxides in a appropriate solvent to give vicinal azidohydrins. Phase-transfer reagents may be used. The reactions usually require high temperatures and/or long reaction times. 

In some cases the ring expansion involves the rearrangement of an azidohydrin intermediate (equation l). 

In synthetic studies on isoprenoid aziridines, Coates and co-workers utilized several Prilezhaev reactions to synthesize epoxides which were reacted with diethylaluminum azide to form azidohydrins.19 Two examples are shown below compounds 27 and 29 were epoxidized using m-CPBA to yield 28 and 30, respectively. 

Vicinal azidohydrins have been prepared by treating epoxides with Et Al/NH in toluene.This mild and selective transformation of... 

In some instances, unprotected glycosyl azides are also suitable precursors for phosphinimines which, in contrast to vicinal azidohydrins, do not... 

Other oxidative double bond azidations have been reported. Thus an azidohydrin was formed from pregnenolone acetate and chromyl azide (NaNs, Chromium(VI) Oxide) and steroidal dienones reacted with TMSNs/Leadf/V) Acetate to give diazido compounds. Vicinal diazides also result from alkenes and Fe Manganese(IH) Acetate (eq 9), or lodosylbenzene and NaNs. Anti-Markovnikov selenoazido products were prepared from the reaction of azide ion with alkenes and (Diace-toxyiodo)benzene/Diphenyl Diselenide (eq 10) a-keto azides (with TMSN3) are formed without PhSeSePh. ... 

---