4H‐1,2‐Oxazete N‐Oxides from 1,1‐Di‐tert‐butylallenes

Abstract

112.0 g of butyl 6ct-fluoro-ll p-hydroxy-16a-methy1-3,20dioxo-l,4-pregnadien-21-oate ( 3 c). Procedure B :A solution of (3c) (5.0g) in n-propanol (300ml) is refluxed with potassium tert-butoxide (250mg) under argon for 1 h. The product is precipitated with 1% acetic acid, filtered off, dried, and recrystallized from acetonehexane. One obtains 2.07g of propyl 6a-fluoro-I 1 ~-hydroxy-16~-methy1-3,20-dioxo-1,4pregnadien-21-oate (39).

The Molecular Mechanism of the Formation of Four-Membered Cyclic Nitronates and Their Retro (3 + 2) Cycloaddition: A DFT Mechanistic Study

“…The Gibbs free energy remains at the same level for 3b , while for 3c , it increases slightly ( Table 1 ). The presented theoretical approach is fully consistent with the experimental work conducted and investigated by Wieser and Berndt [ 6 ]. The GEDT of TS 2a is 0.14 e. In the TS 2a , we observe the rupture of the C1-C2 and N3-O4 single bonds.…”

“…The formation of 4H-[1,2]oxazete 2-oxide ( 3a–c ) derivatives and their retro-32CA reaction experientially investigated by Wieser and Berndt [ 6 ] was theoretically studied at the MPWB1K/6-311G(d,p) computational level. The formation of 4H-[1,2]oxazete 2-oxide ( 3a ) proceeds through a one-step mechanism.…”

“…Cyclic nitronates are an important class of compounds because they pose useful intermediates in the synthesis of complex nitrogen-containing scaffolds due to their high reactivity as 1,3-dipoles and availability from nitroalkenes [ 1 , 2 , 3 , 4 ]. The main methods of obtaining cyclic four-membered nitronates are thermal and photochemical methods involving the cleavage of unsaturated nitro compounds [ 5 , 6 , 7 , 8 , 9 ].…”

“…Wieser and Berndt introduced the thermal methods involving the cleavage of unsaturated nitro compounds leading to four-membered cyclic nitronates [ 6 ]. In the first step they received 3-substituted 4,4-di-tert-butyl-4H-1,2-oxazete N-oxides ( 2a - c ) from a reaction of 1,1-di-tertbutylallenes ( 1a - c ) with dinitrogen tetroxide.…”

Thermolysis of polyazapentadienes. Part 10. Flash vacuum pyrolysis of azoalkenes and some azocarbonyl compounds

“…In fact, none of these events took place when (1) was pyrolysed, and instead HCN was eliminated, by formal cleavage of the two double bonds of the triazapentadiene chain.2 At the time of the preliminary communication,2 such behaviour of non-cyclic azo compounds was unprecedented, ' O though similar reactions had been observed for 2-aza dienes ' and some heteroanalogues. 12 In this paper, we give full details of the pyrolysis of the model compound (l), and of the extension of the work to systems of general formula (5), including simple azo alkenes13 (5; X = R,C) and azo carbonyl compounds'4…”