A azide

A hypervalent iodine(III) reagent, Ph—1=0, together with TMS-azide, promotes direct a-azidation of cyclic sulfides the reaction opens up a route to unstable N,S-acetals. ... 

A further interesting X-ray structural study has been that of (AsPh4)2-[Pd2(N3)6] (66). This reveals similar asymmetry in the two N—N bond lengths for the bridging (1.239 and 1.142 A) and terminal (1.205 and 1.139 A) azide groups. Such structural equivalence indicates that there is no appreciable change in electronic character when a terminal azide co-ordinates to a second Pd via a normally unshared electron pair on the trigonal N atom (see Table... 

Various nucleophilic attacks at C(3) and C(4) of -lactams have been employed to introduce desired functionalities. Nucleophilic displacement of a halogen at C(3) by nucleophiles, for example, potassium phthalimide, has been performed (93JCS(Pl)2357). The a-azidation of l-hydroxy-2-azetidi-nones, for example (37), with arenesulfonyl azides in the presence of triethylamine affords 3-azido-2-azetidinones (38) via Otosylation and SN2 -type of displacement of the tosyloxy group (92JA2741, 93JA548, 93BMC2429). 

Diastereoselective a-azidation via the chiral oxazolidinone auxiliary provides a valuable means of synthesizing highly substituted phenylglycine 46 (Scheme 18).[811... 

There has been intense interest in recent years in selective modification of functionality in baccatin III, 1, the basic diterpenoid core of paclitaxel (Taxol ) which is now established as a clinically active antitumour drug. Given the complexity of 1, rearrangements are common even under mild conditions and attempts to carry out apparently simple transformations are frequently frustrated, as shown by the following example. The 13p-chloro derivative 2 was prepared and fully characterised, then treated with sodium azide in aqueous DMF at 60°C in the expectation that the 13 a azide would be obtained. The product, however, was shown to be the ring cleaved compound 3 (71% yield). 

As expected, Mitsunobu inversion of the allyl alcohol22 using HN3 gave predominantly the a-azide 23 (72). Mild hydrogenation of 23 with 1 atm of hydrogen over Raney Ni produced the corresponding amino compound 24 in a quantitative yield without any significant reduction of the olefin. 

Addition occurred in 2-trimethylsilyloxy-furan upon treatment with PhlO-BF3-Me3SiN3, with direct formation of 5-azidofuranone [99]. Some / -diketones and /j-ketoesters underwent a-azidation by PhIO-Me3SiN3 [100],... 

In situ treatment of 3 with an excess of chlorotrimethylsilane (TMSCI) and subsequent heating affords the a-azide 4 in modest yield and low diastereoselectivity [d.r. (cisjtrans) 40 60]. 

Allylic azides, e.g., 1, were produced by treatment of the triisopropylsilyl enol ethers of cyclic ketones with azidotrimethylsilane and iodosobenzene78, but by lowering the temperature and in the presence of the stable radical 2,2,6,6-tetramethylpiperidine-/V-oxyl (TEMPO), 1-triso-propylsilyloxy-l,2-diazides, e.g., 2, became the predominant product79. The radical mechanism of the reaction was demonstrated. A number of 1,2-diazides (Table 4) were produced in the determined optimum conditions (Method B 16h). The simple diastereoselectivity (trans addition) was complete only with the enol ethers of unsubstituted cycloalkanones or 4-tert-butylcy-clohexanone. This 1,2-bis-azidonation procedure has not been exploited to prepare a-azide ketones, which should be available by simple hydrolysis of the adducts. Instead, the cis-l-triiso-propylsilyloxy-1,2-diazides were applied to the preparation of cw-2-azido tertiary cyclohexanols by selective substitution of the C-l azide group by nucleophiles in the presence of Lewis acids. 

Membranes from S. acidocaldarius (strain 7) catalyze a slow oxidation of NADH. The activity is not significantly affected by antimycin A, azide, or cyanide whereas the oxidation of reduced horse-heart cytochrome c is inhibited by cyanide and azide [16]. Since NADH oxidase activity was assayed by the disappearance of NADH rather than oxygen consumption, this discrepancy probably may reflect an assay that measured the NADH dehydrogenase rather than the oxidase. 

Table 2. The Contributions of Various Electronic Configurations of the MIM model for the State Functions of the PE P model of p-Azidobenzoyloxy Group = Benzo xy Group(B.A.)+Azide(A)...

Figure 7. Infrared spectra of isocyanate formation of model Type C (R = CHS) (Spectrum A, azide and Spectrum B, isocyanate) and of capped lignin-derived polyol.

CsCoupler, A Azide compound, EsExposure time(min.) R Red filter, G Green filter... 

The conversion of methyl (3,4,5-tri-C-acetyl-p-D-araZ)/ o-hex-2-ulopyra-nosyl)onate bromide (51) by sodium azide in Me2SO gave rise to the a-azide 52 in reasonable yield. An alternative approach suggested omission of phase-transfer methods and avoidance of dipolar aprotic solvents, and allowing gly-cosyl halides to react with NaNs in aqueous acetone or acetonitrile. " ... 

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