Hydrazine-hydroquinone complex

The aldehyde/ketone 1 (4.00 mmol), or the ketone 7 (2.00 mmol), or the isothio-cyanate 5 (2.00 mmol) was ball-milled with the solid hydrazine-hydroquinone complex 2 (2.00 mmol) at 25-30 °C for lh (3 h in the case of Id). The yield was quantitative in all cases, as spectroscopically pure mixtures of 3, 6, 8 with 4 were obtained. Hydroquinone 4 was removed by 5 min trituration with 20 mL of water, filtration and three washings with 2 mL of water, each. The residue was dried in a vacuum to obtain the pure products. 4 was recycled from the aqueous washings by evaporation, addition of 1.0 g of 80% hydrazine hydrate in water per 4 mmol of initially reacted 2 and recrystallization to give 520 mg (91%) of pure 2 after filtration, washing with water and drying. 

Kaupp and Schmeyers subjected to ball milling the solid aldehydes and ketones with the hydrazine-hydroquinone complex 83 in a 2 1 ratio to obtain azines 84 at room temperature (Scheme 3.22) [19]. Experiments were carried out in Retsch MM2(X)... 

Kaupp G, Schmeyers J. Solid-state reactivity of the hydrazine-hydroquinone complex. J Phys Org Ghem 2000 13 388-94. 

NOTE Cupric copper (Cu2+) is a catalyst for the hydrazine-oxygen reaction, as well as a catalyst for sulfite, DEHA, erythorbic acid, and hydroquinone. Cuprous copper (Cu+) acts as a complexing agent in the desirable formation of protective, pasivated copper oxide films. 

A mixture of powdered dimethyl terephthalate la (19.4 g, 0.1 mol) and 1 1 inclusion complex of hydroquinone and hydrazine (58.5 g, 0.4 mol) was kept under a nitrogen atmosphere at 100-125 °C for 25 h. To the reaction mixture was added MeOH and MeOH insoluble terephthalic acid dihydrazide 2a was obtained by filtration (17.1 g, 88.1% yield). 

The inclusion complex of an unstable reactant or reagent is sometimes useful in organic synthesis in the solid state. For example, very reactive anhydrous hydrazine can be trapped as a 1 1 inclusion complex with hydroquinone (24). This 1 1 inclusion compound (24) is a stable white powder that can easily be prepared by mixing aqueous hydrazine with powdered hydroquinone. Compound 24 is... 

The H-bonded sheets create distorted super-cyclohexane boats (and not chairs ) that are neither zincblende-nor wurtzite-like super-structures. A careful revision of the literature reveals other interesting examples of super-structures formed by alcohols and amines. For example, during their studies dealing with the preparation of a stable form of hydrazine, Toda and co-workers [41] reported the formation of the supramolecular 1 1 amine-alcohol complex 1 3 between hydrazine (1) and hydroquinone (3) (Scheme 3). 

Scheme 3 Preparation of the complex 1 3 between hydrazine 1 and hydroquinone 3.

In the crystal of complex 1 3, hydroquinone and hydrazine molecules form an extensive H-bonding network in which all oxygen and nitrogen atoms are fully coordinated in a super-tetrahedral architecture. In this aggregate, the amino and... 

The structure found for 14 15 appears to be closely related to that of a previously described complex between hydrazine and hydroquinone, as evidenced by the similar constant lattice and space group. The authors [41] considered the complex 14 15 as formally generated by the replacement of one of the hydrophilic regions located on both sides of the complex between hydrazine and hydroquinone by the 4-meth-oxy groups (Figure 22). Crystallographic twofold axes characterize the H-bonding network around the hydrazine molecules. 

Figure 20 Crystal packing of the complex 1 3 between hydrazine (1) and hydroquinone (3). Thin lines illustrate H-bonds [41].

Alternatively, under strong reductive conditions, e.g. electrochemical reduction, arylpalladium(II) halide (XIII) is reduced to arylpalladium(0) which, upon the second oxidative addition, gives diarylpalladium(II) complex, also capable of undergoing reductive elimination of biaryl similarly to XIV [10]. Isopropanol [50-52], amines [4,17,52-54], hydrazine [55], tetrakis(dimethylamino)ethylene [18], hydroquinone [56], tetrabutylammonium ftuoride [57], formates [58-60], zinc [61-64], and molecular hydrogen [65] have been used as stoichiometric reductants. Electro-reductive homocoupling of aryl halides was also reported [10]. The most important methods for... 

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