Oxygen diethyl azodicarboxylate

An alternative to activating the nitro moiety by forming the nitronate salt is the activation of an oxygen leaving group under Mitsunobu conditions (Eq. 2.15) (155,156). Treatment of methanol with diethyl azodicarboxylate and triphenyl-phosphine in the presence of ethyl nitroacetate provides the nitronate 85 in good yield. Unfortunately, only methanol has been demonstrated to be compatible with this procedure. 

Macrolactonization can also be achieved by the Mitsunobu reaction [44] with inversion of the configuration of the alcohol. The reaction principle and mechanism are demonstrated in Scheme 24. Addition of triphenylphosphine to diethyl azodicarboxylate (DEAD, 73) forms a quaternary phosphonium salt 74, which is protonated by hydroxy acid 11, followed by phosphorus transfer from nitrogen to oxygen yielding the alkoxyphosphonium salt 76 and diethyl hydrazinedicarboxy-late 75. Then, an intramolecular Sn2 displacement of the important intermediate 76 results in the formation of the lactone 15 and triphenylphosphine oxide. 

Their preparations copied those of their [ ]-analogues. The first method started from 2-hydrazinopurines 287 and suitable ortho esters yielding [l,2,4]triazolo-[4,3- ]purin-9-ones 288 (R2 = Aik, Aryl). Substitution of ortho esters by carbon disulfide led to 7-mercapto-derivative 288 (R2 = SH). The 7-aryl-derivatives were better accessible by the second method—the oxidative cyclization of 2-arylidenehydrazino)-derivatives 289, such as heating with diethyl azodicarboxylate, or oxidation with aerial oxygen (85CPB3113) (Scheme 82). 

Heterodienophiles have also been studied diethyl azodicarboxylate adds across the 2,6-positions of a pyridazin-3-one, and singlet oxygen across the 2,5-positions of pyrazinones. The immediate cycloadduct is isolable when acryloyl cyanide is used as the heterodiene component in reaction with a pyrimidine-2,4-dione. ... 

Oxepan and other oxygen- or nitrogen-containing saturated heterocycles can be prepared in high yield by the dehydrative coupling of aamino-alcohols, using diethyl azodicarboxylate and triphenylphosphine. The synthetically useful oxepin-2,7-diones (muconic acid anhydrides) can be conveniently prepared by the oxidation of ortho-henzoquinones with w-chloroperoxybenzoic acid. °... 

Diethyl azodicarboxylate reacts smoothly with a wide variety of alcohols, mercaptans, anilines, and hydrazobenzenes to form 0x0 compounds, disulfides, and azobenzenes. The reaction does not proceed further after abstraction of hydrogen because the reagent has no oxygen atoms available for oxidation. F. e. and procedures s. F. Yoneda, K. Suzuki, and Y. Nitta, Am. Soc. 88, 2328 (1966) improved yields of ketones with A-phenyl ly2,A-triazoline 3,5-dione s. R. C. Cookson I. D. R. Stevens, and C. T. Watts, Chem. Gommun. 1966, 744. 

The preparation of N-alkoxy derivatives (i.e., type V) is somewhat more difficult They can be prepared by treatment of the sodium salt of 2-mercaptopyridine-N-oxide with 1 molar equivalent of the suitable alkyl halide in DMF at 80°C. ° By using this coupling reaction, alkylation occurs at sulfur rather than at oxygen, and the reaction affords pyridyl sulfides as the major product. In such cases, the Mitsonobu method using diethyl azodicarboxylate and triphenylphosphine may provide a solution (Scheme 8). ... 

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