Nitriles from nitro compounds

Macro carbocyclic rings can be constructed by cyclization of nitrile oxides derived from oj-nitro-l-al-kenes (Scheme 22). If the intervening bridge is not longer than seven atoms, only fused bicyclic products are obtained. Thus, the nitrile oxide derived from nitro compound (75a) is cyclized in 44% yield to the 5,9-fused bicyclic isoxazoline (76a).38 10-Nitro-l-decene (75b) also cyclized to (76b) in unspecified yield.39 It should be noted that these results go counter to the usual regiochemistry of an intermolecular nitrile oxide cycloaddition where the five-substituted isoxazoline is usually,27 although not always,40 heavily preferred from reaction of a terminal alkene. Thus, geometric constraints have won out over the normal electronic control. 

Many substrates containing a cyclic bridge have been investigated in intramolecular nitrile oxide cycloadditions. Typical examples include cyclization of the nitrile oxides derived from nitro compounds (91) and (92 Scheme 26).44 MM2 calculations are consistent with these results a chair-like transition state led to formation of the 5,6-fused product (93). Cyclization of (92) occurred through a more flexible... 

DC of acetylenes 6 and nitrile oxides, generated in situ from nitro compounds 5, afforded isoxazoles 7 directly (R3 = Ar) or through Stifle coupling with aryl iodides of the 5-... 

A simultaneous reduction-oxidation sequence of hydroxy carbonyl substrates in the Meerwein-Ponndorf-Verley reduction can be accomplished by use of a catalytic amount of (2,7-dimethyl-l,8-biphenylenedioxy)bis(dimethylaluminum) (8) [33], This is an efficient hydride transfer from the sec-alcohol moiety to the remote carbonyl group and, because of its insensitivity to other functionalities, should find vast potential in the synthesis of complex polyfunctional molecules, including natural and unnatural products. Thus, treatment of hydroxy aldehyde 18 with 8 (5 mol%) in CH2CI2 at 21 °C for 12 h resulted in formation of hydroxy ketone 19 in 78 % yield. As expected, the use of 25 mol% 8 enhanced the rate and the chemical yield was increased to 92 %. A similar tendency was observed with the cyclohexanone derivative. It should be noted that the present reduction-oxidation sequence is highly chemoselective, and can be utilized in the presence of other functionalities such as esters, amides, rert-alco-hols, nitriles and nitro compounds, as depicted in Sch. 10. 

Hydrolysis of nitriles yields carboxylic acids. The synthesis of nitriles from diazonium salts thus provides us with an excellent route from nitro compounds to carboxylic acids. For example ... 

Solid-phase synthesis of 3-hydroxymethyl isoxazoles 17 was accomplished in acceptable yields and purity through 1,3-DC of different alkynes 15 to resin bound nitrile oxides, generated from nitro compounds 14 under Mukaiyama conditions. This method is robust enough to be carried out by an automated synthesiser <01TL4951>. 

There are rather few water-soluble hydrogenation catalysts. A number of rhodium complexes derived from ligands such as (PH2PCH2CH2)2NC0C6H4S03" are active in this way. " Catalysts have been developed for hydrogenation of ketonescarboxylic acids/ esters/ nitriles/ and nitro compounds. 

The two major methods of preparation are the cycloaddition of nitrile oxides to alkenes and the reaction of a,/3-unsaturated ketones with hydroxylamines. Additional methods include reaction of /3-haloketones and hydroxylamine, the reaction of ylides with nitrile oxides by activation of alkyl nitro compounds from isoxazoline AT-oxides (methoxides, etc.) and miscellaneous syntheses (62HC(i7)i). 

Alkali metal reduction is a widely employed method for the preparation of radicals derived from various classes of conjugated compounds such as hydrocarbons, heterocycles, nitro compounds, quinones, and nitriles. For... 

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