1- Aza-1,3-dienes

A numher of azabenzisochromanquinone antibiotics have been synthesised by the HDA reaction between isochromanquinones and 1-aza-1,3-dienes <96LA1385>. 

A cobalt catalysed carbonylation reaction converts A-substituted 1-aza-1,3-dienes into A-allylacetamides by a reductive acylation process [31]. Acetamides are byproducts of the reaction. In contrast, Schiff bases undergo a double A,C-acetylation under the same conditions producing a-acetamido ketones and A,A-disubstituted acetamides [32],... 

Finally, reaction of 2,4-diphenyl-5(4//)-oxazolone 322 with 4-phenyl-A -tosyl-1-azabuta-1,3-diene was found to be highly dependent on the experimental conditions. At room temperature the sole product was 323 that arises from alkylation of 322 by addition at the imine carbon. However, heating 322 and 4-phenyl-A-tosyl-1-azabuta-1,3-diene gave rise to several products including a 2-pyridone 324, 2,3,6-triphenylpyridine 325, and the pentasubstituted pyrroles 326 and 327. The authors postulated two different reaction mechanisms. Here, both a 1,3-dipolar cycloaddition of the oxazolone and a nucleophilic addition of the oxazolone are possible and that may account for the formation of 324—327. The marked differences in reactivity of 4-phenyl-A-tosyl-l-azabuta-l,3-diene relative to A-alkyl- or A-aryl-1-aza-1,3-dienes was attributed to the powerful electron-withdrawing nature of the tosyl group (Scheme 7.107). ... 

Reduction of TiCLi(THF)2 with 2 equivalents of Mg in the presence of 2 equivalents of a sterically demanding 1-aza-1,3-diene, ArN=CHC(CH3)=CAr (Ar=l,5 (i-pr)2C6H3), gives the homoleptic early transition metal 1-aza-1,3-diene complex, Ti(l-aza-l,3-diene)2. X-ray diffraction analysis of this complex shows Ti-N distances of 1.949(2) and 1.939(2)A and Ti-C distances of 2.317(3) and 2.132(3) A. The subsequent addition of MeLi and elimination of methane... 

AmUnotetruhydrofurans The complexes derived from Cp Zr and 1 -aza-1,3-dienes insert carbonyl compounds which on demetallation with pyridine Al-oxide lead to 2-anilinotetrahydrofurans, and thence to the y-lactols and other compounds. 

CpTiCl3 reacts with Mg in the presence of 1-aza- 1,3-dienes to give the corresponding aza-titanacyclopentene derivatives, isolated as air sensitive green-brown crystals. Treatment of these compounds with LiMe leads to the... 

A general synthesis of 3,5-disubstituted pyridines is based on the uncatalysed thermal reaction of imines with enamines which yields 1-aza-1,3-dienes. The dienes afford the pyridines by a further reaction with the same or a different enamine. For example, methylene A- -butylimine (304) and 1-piperidinobutene give the diene 307, accompanied by 3,5-diethylpyridine (309 = Et) Heating the diene with 1-piperidinopropene gives... 

Under a CO atmosphere and in the presence of Ru2(CO),2, 1-aza-1,3-dienes are converted to unsaturated y-lactams. Bicyclic lactams are formed in the reaction of... 

S-Unsaturated hydrazones such as (12) have been shown to behave as 1 -aza-1, 3-dienes in Diels-Alder addition reactions with a range of dienophiles such as maleic anhydride (Scheme 2). The dimethylamino substituent in the cycloadducts (e.g. 13) may be cleaved by treatment with zinc and acetic acid, but no conditions have so far been found to cleave the N-N bond without reducing the C-C double bond 5-Nitropyrimidine undergoes inverse Diels-Alder cycloaddition with electron-rich dienophiles such as enamines and ketene N,N- and 0,0-acetals (Scheme 3). ... 

Cyanation. 1-Aza-1,3-dienes are cyanated at C-2 by treatment with Me SiCN and chromium(VI) oxide. ... 

More recently (2004), Joule proposed a novel synthetic route to access the akuammiline scaffold with reports from his group s synthetic efforts toward realizing this plan. Retrosynthetically, they envisioned akuammiline (1) to result from late stage imine formation of ketone 247 (Scheme 32). The functionality at position 16 would then be elaborated from a carbonyl contained in diketone 248, which in turn was planned to be obtained via an intramolecular Claisen condensation and double bond isomerization of enamine 249, the latter the product of an aza-Diels—Alder cycloaddition involving cyclic 1-aza-1,3-diene 250 and an acrylate 251. To access azadiene 250 they planned an oxidative ring opening of bicyclic pyrrole 252. 

Morpholino-1,3-dienes can be obtained by selective amino-mercuration of the alkynyl bond of alk-3-en-1-ynes. Catalytic amounts of Hg(0Ac)2 in dry tetrahydrofuran appear to be the optimum conditions for this reaction to occur rather than 1-aza-1,3-diene formation, which occurs with HgCl and potassium carbonate in aqueous tetrahydrofuran. 4-Amino-1,1-dicyanobuta-1,3-dienes... 

Palladous acetate has been found to catalyse addition of cyano-trimethyIsilane to 1-aza-1,3-dienes in dichloromethane, this... 

The increasing use of azabutadiene systems in synthesis has led to renewed efforts directed towards their synthesis. oi,B-Ethyl-eneimines(1-aza-1,3-dienes ) were prepared by simple additions of amines to 1,3-enynes mediated by mercury(II) chloride and potassium carbonate in wet tetrahydrofuran (THF-H O 1 ). Elsewhere... 

Scheme 1.20 Inverse-electron-demand Diels-Alder cycloaddition of iV-sulfonyl-1-aza-1,3-dienes with vinyl ethers.

A novel series of Ni-alkene complexes 14—17 has been prepared with 1-aza-1,3-dienes acting as terminal or bridging ligands that coordinate Ni(0) centers in rf C,C) r] (N) fashion." Gomplexes 14 are very air sensitive, thermally unstable, deep blue compounds that react with PPh3 to produce the dimeric species 15 (deep red). In contrast, reactions... 

Aza-1,3-dienes undergo [4 + 3] cycloaddition with Pd-TMM providing azepane derivatives (eq 34). ... 

Likewise, imidoyl ketenimines 153 react as 1-aza-1,3-dienes in [4-1-2] cycloaddition reactions with phenyl isocyanate to give the cycloadducts 154 (62-67 % yields) or with tosyl isothiocyanate to give the cycloadducts 155 (62-69 % yields) . ... 

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