Halogen azide additions

Free Radical Additions I. Halogen azide additions 

The possibility of both homolytic and heterolytic cleavage of halogen azides has previously been discussed (section IV.E.l). Such additions may be observed in solvents of low polarity, in the presence of light and the absence of radical trapping species such as oxygen 

Styrene, for example, is known to add both bromine and chlorine azide quantitatively and regiospecifically under such conditions to give the adduct (223 X=Br, Cl). This is consistent with an initial 

This reaction has been utilized in the synthesis of azidosteroids . Addition to 2-cholestene (224) occurs regioselectively and adducts 225 and 226 have been isolated in 37% and 27% yield respectively. By comparison, ionic addition leads to the /ranj-diaxial product (227). Such differing orientations of the products obtained from homolytic and heterolytic addition may be synthetically valuable. 

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Iodine isocyanate addition to olefins / 22 Halogen azide addition to olefins / 24 Via epoxides and / -mesyloxy azides / 27 By addition of alkoxyamines / 29... 

F. Free Radical Additions I. Halogen azide additions... 

March76 has provided a valuable summary of the work on additions of halogen azides to olefinic double bonds to provide / -halo azides (e.g. equation 52) the summary is based... 

The present situation in regard to addition of halogen azide to alkynes is that the synthetic aspects are well established but that mechanistic evidence is sparse and equivocal. Clearly, some rate studies of diese reactions would be of value in elucidating the mechanisms actually involved. 

Binary Halides. In addition to NF3, NF2C1, NFC12 and NC13, we have N2F2, N2F4 and the halogen azides XN3 (X = F, Cl, Br or I). With the exception of NF3 the halides are reactive, potentially hazardous substances, some of them like NFC12 explosive, others not. Only the fluorides are important.35... 

An additional absorption band at 2164 cm was interpreted as an overtone 2vs [4]. The position of frequencies and the weaker N-halogen bond were compared to those of the other halogen azides [7]. 

That looks simple and direct don t it If safrole was used as the alkene one would get safrole-azide as product. Just one teensy little reduction away from MDA. Strike also found some azide papers that, with a little work, will get safrole-azide in a totally different way. Strike came across a lot of work where groups were using dinucleophilic addition to get an azide and a halogen added across a double bond. The azide would always go to the beta secondary carbon and the halogen to the primary carbon (just what one would want if safrole was the substrate). 

The effect of a substituent may be substantially modified by fast, concurrent, reversible addition of the nucleophile to an electrophilic center in the substituent. Ortho- and para-CS.0 and pam-CN groups have been found by Miller and co-workers to have a much reduced activating effect on the displacement of halogen in 2-nitrohaloben-zenes with methoxide ion [reversible formation of hemiacetal (143) and imido ester anions (144)] than with azide ion (less interaction) or thiocyanate (little, if any, interaction). Formation of 0-acyl derivatives of 0x0 derivatives or of A-oxides, hydrogen bonding to these moieties, and ionization of substituents are other examples of reversible and often relatively complete modifications under reaction conditions. If the interaction is irreversible, such as hydrolysis of a... 

The utilization of a-amino acids and their derived 6-araino alcohols in asymmetric synthesis has been extensive. A number of procedures have been reported for the reduction of a variety of amino acid derivatives however, the direct reduction of a-am1no acids with borane has proven to be exceptionally convenient for laboratory-scale reactions. These reductions characteristically proceed in high yield with no perceptible racemization. The resulting p-amino alcohols can, in turn, be transformed into oxazolidinones, which have proven to be versatile chiral auxiliaries. Besides the highly diastereoselective aldol addition reactions, enolates of N-acyl oxazolidinones have been used in conjunction with asymmetric alkylations, halogenations, hydroxylations, acylations, and azide transfer processes, all of which proceed with excellent levels of stereoselectivity. 

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