Oxetanes, azido

BAMO is perhaps the most prominent among the azido oxetanes class in terms of the number of polymers and copolymers reported so far. Due to its symmetrical azido groups, it assumes special significance as a hard block repeating unit in a thermoplastic elastomer. However, the homopolymer is solid and cannot be used directly for binder applications because of its crystal-tine nature. Also, poly(BAMO) shows relatively poor mechanical properties as a binder for solid rocket propellants [153]. Many copolymers of BAMO with non-energetic co-monomers tike tetrahydrofuran (THF) have been reported. The BAMO-THF copolymer is an excellent candidate for binder applications with its energetic BAMO content coupled with the THF block which affords... 

Several different nucleophilic displacement reactions of ring substituents were utilized in the synthesis of 3-azido-oxetane-2-carboxylates (Scheme 12) <2001TL4247>. The triflate ester 66, prepared from the corresponding trans-/3-hydroxy ester and triflic anhydride, was displaced by reaction with sodium azide, and inversion of configuration, to... 

Xylonolactone 95, embodying an azide functionality, was submitted to the ring contraction conditions to determine whether it was possible to access 5-azidooxetanes in a smaller number of steps 5-azido oxetanes (Scheme 4.15). While 96 was obtained in a 67% yield, ring contraction of its epimer 98 afforded a mixture of the a and p anomers isolated in a 57% yield for 99 and a 7% yield for 101. Azide reduction and ester hydrolysis afforded Boc protected 8-amino acids in a good yield [37]. 

The energetic nature of the azido group makes its incorporation into energetic polymers and binders very desirable. 3,3-Bis(azidomethyl)oxetane (BAMO) (28) and 3-azidomethyl-3-methyloxetane (AMMO) (33) are energetic monomers which on polymerization result in the energetic polymers poly[BAMO] (32) and Poly[AMMO] (34), respectively, both of which are under evaluation as potential energetic alternatives to HTPB in composite propellant formulations. ... 

Epoxy sugars are frequently used as starting compounds in the synthesis of sugar derivatives (compare Section IV) such as halo, amino, azido, thio, deoxy, and branched-chain derivatives. The oxirane ring is in general more reactive than the oxetane or oxolane ring. It is opened with nucleophiles under base or acid catalysis. On the other hand, the oxirane ring remains unattacked under the conditions of catalytic debenzylation on palladium,... 

The constrained nucleosides are of interest as leads for small-molecule therapeutics. For example, the (3-2 -0,3 -C-oxetane analogues of the antiviral 3 -azido-3 -deoxythymidine (AZT), which exist predominantly in the E-like conformation (see, for example, Equation 55), were investigated for inhibition of human immunodeficiency virus 1 (HIV-1). Neither the modified nucleosides nor their 5 -monophosphate analogues inhibit HIV-1, supporting a hypothesis that reverse transcriptase inhibitors must have conformational freedom <2001JOC4878, 2002J(P1)1655>. 

The application of azido polymers, (e.g., poly(glycidyl azide), poly(azidomethyl methyl-oxetane) and poly(bisazidomethyl oxetane) as binders and fnels in rocket technology is well documented. The high energy release upon the decomposition of the azide group of these polymers is responsible for their specialised application... 

Polymers used as energetic binders should act not only as a binder but also as a real propellant component. Thus most frequently azido groups having a tendency to highly exothermic decomposition are introduced into a side chain. Oxetane... 

Oxetane 8-amino acids and their 5-azido ester precursors have been submitted to a number of transformations, showing the synthetic potential of these stmctures. 1,2,4-Oxadiazole, commonly used as bioisosteric replacement for amides, esters, and isothioureas [38] was introduced into stmctures type 103 [39] (Scheme 4.16). 

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