Alkyl-substituted azides

There is evidence from a detailed study of the photolyses of 2-alkyl-substituted aryl azides 40 in diethylamine that A3,7V-diethyl-1 //-azepin-2-amines are formed as oxygen-sensitive, meta-stablc intermediates that can give rise to a variety of byproducts, including 5-acyl- A%V-diethyl-pyridin-2-amines and 6-alkyl-7-(diethylamino)-2//-azepin-2-ones 11 however, formation of these oxidation products can be avoided by refluxing the photolysate mixture with methanol prior to exposure to oxygen, in which case practicable yields of the /V,/V-diethyl-3W-azepin-2-amines 41 result. 

Aryldioxophosphoranes such as aryl- and alkyl-iminooxophosphoranes number among the short-lived metaphosphonates. The former are best obtained by fragmentation of cyclic phosphinic esters, and the latter by rearrangement of aryl- and alkyl-substituted phosphoryl azides and nitrenes, respectively. This reaction is reminiscent of the phosphorylcarbene/methyleneoxophosphorane rearrangement discussed in Section 2. 

The addition of methanol or hydrazoic acid to ethenylidenecydopentadiene 3 demonstrates that 3 behaves like an acceptor-substituted allene (Scheme 7.27) [226, 227]. More examples of nudeophilic additions to alkyl-substituted derivatives of 3 were reported by Hafner [228]. Photoelectron spectroscopy of the spirocyclic compound 165b, easily accessible from azide 164b, shows that the lone-pair orbital n(N) of the 2H-azirine nitrogen atom interacts strongly with the Jt1-orbital of the cyclo-pentadiene ring [227]. 

Nucleophile substitution of the T1 resin synthesis of phenols, biaryls, alkyl arenes, azides, aromatic hydrazines, halides, ester, azo compounds cinnolines, benzotriazoles [129-137, 140, 141]... 

Substituted anhydro-5-hydroxy-l,2,3,4-oxatriazolium hydroxides (4) decompose on heating in strong acids <320912,56JA5124>. The 3-alkyl substituted compounds produce carbon dioxide, azo-imide (HN3), and the alcohol corresponding to the 3-substituent. The 3-aryl substituted analogues produce carbon dioxide and aryl azide. In some cases the initially formed aryl azide decomposes further to anilines under the conditions of the reaction <82JCS(P2)70l>. Kinetic studies indicate that 3-methyl-anhydro-5-hydroxy-l,2,3,4-oxatriazolium hydroxide (24) reacts via a bimolecular A-2... 

Typical 1,3-dipolar cycloreversion is found for the decomposition of alkyl-substituted 2-tetrazolines (43) (88CB1213), l,4-dihydro-l,2,3,4-tetrazol-5-ones (44), and -thiones (45) (97JHC113). For these reactions two paths are possible that can be distinguished when the substituents on N-l and N-4 are different. For 2-tetrazolines ring contraction leading to diaziridines is also possible (discussed earlier). Cycloreversion of 43 yields imines and azides (88CB1213). 

However, one typical example of a silane, alkyl-substituted silane, silyl azide, silyamine, siloxane and a silane polysulfide polymer, which is or can possibly be used in ordn areas, is presented next. Substituted siloxanes are defined and presented separately under Silicones ... 

VO(OR)3 are very convenient and easily available precursors for the preparation of a wide range of V(V) derivatives and via their reduction by matalla-lkyls even for the derivatives of the lower oxidation states. The complete or partial substitution of OR-groups has led to halides, carboxylales, P-diketo-nates, alkyls, sulfides, azids, complexes with Shiffbases, phenylisocyanate, and so on. Hydrolysis of VO(OR)3 is discussed in Chapter 9. 

The procedure is essentially similar to that described for the preparation of 5-amino-l,2,3,4-thiatriazole. Freund and Hempel6,7 have reported observing that the initial diazotization products of 4-aryl-substituted thiosemicarba-zides lead to the formation of tetrazoles, while the corresponding 4-alkyl-substituted thiosemicarbazides were considered by Freund and Schwarz8 to be thiatriazoles. However, Oliveri-Mandala,9 on the basis of his study of the reaction of alkyl and aryl isothiocyanates with hydrazoic acid, concluded that the initial diazotization product of either 4-aryl or 4-alkyl thiosemicarbazides were open-chain thiocarbamyl azides, RNHC( S)N3. Lieber, Pillai, and Hites10 have recently clarified this situation and have shown... 

The difficulty in trying to forecast which way round a 1,3-dipolar cycloaddition will go is well illustrated when a substituted azide adds to an alkyne in the synthesis of 1,2,3-triazolcs. Reaction of an alkyl azide with an unsymmetrical alkyne, having an electron-withdrawing group at one end and an alkyl group at the other, gives mostly a single triazole. 

Aliphatic azides undergo a little known allylic-type rearrangement (reaction 81). This has been studied in a variety of solvents for R = metliyl and hydrogen and the percentages of the isomers at equilibrium have been measured In contrast to the analogous iso-merizations of allylic chlorides the rates of rearrangement are insensitive both to alkyl substitution and to solvent and no accompanying... 

Addition of iodine azide to 1-alkylcyclobutenes gave good yields of 1 -alkyl-substituted trans-1-azido-2-iodocyclobutanes. 

The disadvantage of this method for synthesizing 1-aryl-substituted A -tetrazoline-5-ones is the fact that three equivalents of sodium azide per equivalent isocyanate are required [ 102]. To circumvent this drawback, a process for the generation of 1-aryl- and 1-alkyl-substituted A -tetrazoline-5-ones was developed that uses equimolar amounts of sodium azide, aluminum chloride and the corresponding isocyanate in DMF as solvent. Heating of this three component mixture for 2 to 24 hours followed by treatment with dilute hydrochloric acid provides the 1-aryl- and 1-alkyl-substituted A -tetrazoline-5-ones, respectively [103]. 

Alkylation of Azide Ion and Reduction A much better method for preparing a primary amine from an alkyl halide is first to convert the alkyl halide to an alkyl azide (R — N3) by a nucleophilic substitution reaction, then reduce the azide to a primary amine with lithium aluminum hydride. 

It was recently suggested that for alkyl or aryl substituted azides, most agreed that the concerted mechanism was likely the case. However, when salts of hydrazoic acid are used (as ionic azide is not a 1,3-dipole), or when a strongly EWG is attached to the nitrile, many authors still favor the stepwise process based on computational and experimental evaluation. ... 

In 1999, Jacobsen reported on a catalytic asymmetric conjugated addition of hydrazoic acid to unsaturated imide derivatives (Equation 4.1). This breakthrough was possible through the use of aluminium salen azide complex 1 as catalyst. The reaction proceeded in excellent yields and enantioselectivities for alkyl substituted acceptors. Two mechanisms were proposed for this reaction activation of the azide as an aluminium azide as shown by Chung and co-workers or Lewis acid activation of the imide. The first-order dependence of the rate law on catalyst 1 indicated that dual activation was improbable. In 2005, Jacobsen reported on the extension of this methodology to ,j8-unsaturated ketones. 

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