Azido isocyanates

For the synthesis of chloro- (azido-, isocyanate-, isothiocyanate-)silyldiazoacetic esters 6-9, the same strategy has been used, but with chlorosilyl triflates as starting materials [12] (Scheme 2). 

Scheme 2. Synthesis of chloro- (azido-, isocyanate-, isodiiocyanate-)silyldiazoacetic esters...

Iodine azide, on the other hand, forms pure adducts with A -, A - and A -steroids by a mechanism analogous to that proposed for iodine isocyanate additions. Reduction of such adducts can lead to aziridines. However, most reducing agents effect elimination of the elements of iodine azide from the /mwj -diaxial adducts of the A - and A -olefins rather than reduction of the azide function to the iodo amine. Thus, this sequence appears to be of little value for the synthesis of A-, B- or C-ring aziridines. It is worthy to note that based on experience with nonsteroidal systems the application of electrophilic reducing agents such as diborane or lithium aluminum hydride-aluminum chloride may yet prove effective for the desired reduction. Lithium aluminum hydride accomplishes aziridine formation from the A -adducts, Le., 16 -azido-17a-iodoandrostanes (97) in a one-step reaction. The scope of this addition has been considerably enhanced by the recent... 

Bei dieser Aufbauvariante des 1,2,4-Oxadiazol-Ringes stellt die Komponente O—C — N-C den Teil eines Acyl-isocyanates dar, das mit Azido-trimethyl-silan als N-Lieferant formal das Het-aren bildet. 

Isocyanate Benzoyl Azide. See 2 Azido-formylphenylisocyanate in Vol 1, p A638-R... 

The reversed reaction, i.e. attack of CO on the corresponding transition metal azido complex, sometimes also provides an attractive route for the synthesis of isocyanate complexes, e.g. the reaction of CO with, for example, Co(N3)(DH)2(PPh3),344 Rh(f/5-C5Me5)(N3)4276 or Rh(N3)(cod).344... 

In order to classify the reactive building blocks, we grouped them into mono-and bidentate nucleophiles (e.g. amines, alcohols, thioureas, isothioureas, amidi-nes, amidrazones), into their mono- and bis-acceptor counter parts (e.g. alkyl halides, a-bromomethyl ketones, a-alkinyl ketones), and into donor-acceptor species (e.g. isocyanates, isothiocyanates, 2-azido benzoic acids215), as depicted in Figure 40. 

The alkene pseudohalogen adducts (15) of Scheme 8 are also useful intermediates for aziridine synthesis. These adducts are discussed later in Sections 3.5.6.2-4. The iodine azide " and bromine azide ° adducts may be reduced to aziridines with many reagents recent references report use of lithium aluminum hydride and dimethylamineborane. TTie iodine isocyanate aziridination continues to prove useful, as in Scheme 10. Since the recent reviews, - the mechanism of the triphenylphosphine-based cyclization of azido alcohols has appeared (Scheme 11) there are clear steric consequences. Alkenes can be chlorinated in acetonitrile to give intermediates which can be worked up to yield aziridines (Scheme 12). ... 

Acyloxy-l-isocyan- E14a/2, 200 (Keton/R- CO - X/AgCN) 1-Alkoxy-l-azido- EI4a/2, 117 (OR - N3), 290 (En-OSiR3 + HN3/R-OH)... 

Trifluoromethyl)quinazolin-4(3//)-one (6) is formed quantitatively from a-azido-a-phenyl-/1-trifluoroethyl isocyanate (3) via a nitrene intermediate 4 which undergoes rearrangement to a-(A -phenylimino)- 8-trifluoroethyl isocyanate (5) followed by cyclization to 6 (cf. p 58). °... 

Isocyanate Benzoylazide. See 2-Azido-formylphenylisocyanate A63 R Iso-Me-NENA, See Nitraminopropanol Nitrate under Aminopropanols A253 L... 

Treatment of a-azido esters 1290 with triphenylphosphine gives -phosphazides 1291, which subsequently react with isothiocyanates to afford thiohydantoins 1292 after aqueous work-up. The cyclization conditions can also be adapted to hydantoin synthesis when isocyanates are used (Scheme 328) <2004TL1655>. 

Very recently, amino deoxyglucmonic acids were used in the construction of disaccharide libraries [45]. In the report, methyl 3-azido-3-deoxy-4-0-methyl-j8-D-glucmonic acid was prepared and glycosidically linked to a protected glucosamine, yielding a disaccharide with both amino and carboxamide fimctionalities. The azide was subsequently reduced and reacted with several isocyanates, providing libraries of j8-linked disaccharides (Fig. 24). 

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