Reactions, with nitriles

Reaction with Nitriles. Nitriles are carboxylic acid derivatives and react with Grignard reagents (also sec, 8.2.C).l Initial attack generates an intermediate iminium salt that can be hydrolyzed (with loss of ammonia) to the corresponding ketone. HO The best yields are obtained with aryl nitriles, and this is illustrated 

1 Formation of Pyridines, Pyrroles, A -Bipyrrolines, Siloles, and (Z, Z)-Dienylsilanes Remarkable E ect of Substitution Patterns on the Butadienyl Skeletons 

Mechanisms on the reactions of 1,4-dilithio-l,3-butadienes and nitriles were explored through DPT calculations [65]. The computational results again support that the selectivity of these reactions is strongly affected by the stractures of the substrates. As the first step of all reaction pathways, one C-Li bond reacts with the nitrile to give the A-Uthio ketimine intermediate. 

When tetra-alkyl substituted 1,4-dilithio-l,3-dienes and 2-cyanopyridine are used, the A-Uthio ketimine intermediate undergoes 5-exo cyclization to give the cyclopentadienyl amine 42 as the kinetic product because of the coordination of the pyridyl A -atom to the lithium atoms. 

When tetra-alkyl substituted 1,4-dUithio-l,3-dienes and aryl nitriles are used, the Wlithio ketimine intermediate undergoes insertion of a second nitrile into the C-Li bond to afford the 1,8-dilithio bis-ketimine intermediate. 1,8-Dilithio bis-ketimine 

When cyclic 1,4-dilithio butadiene and tertiary aliphatic nitriles are used, the 1,8-dilithio bis-ketimine intermediate undergoes two sequential 1,5-cycUzatiOTi steps with a lower energy barrier, generating tricyclic A -bipyrrolines 44. The calculation results clearly show the mechanism details and are in good agreement with the experimental observations [65]. 

---

Propanediol and its derivatives yield 5,6-dihydro-l,3-4/f-oxa-zines (36) by reaction with nitriles in the presence of sulfuric... 

Thioazadienes 90, formed in situ by the reaction of trimethylsilylimines and isothiocyanates, underwent cycloaddition reactions with nitriles bearing electron-withdrawing groups, to afford 1,3,5-thiadiazines [94] in excellent yield (Equation 2.26). 

Reaction with nitrile and phosphine complexes 6.5.3.1 C4 Bf3 FeGaNa 2O4 Na2[(CO)4FeGaBr3]... 

Polymers derived from the preceding type of reaction with nitriles,5 amines,6 and phosphines,7 have been reported. Green8 has reported the preparation of a resin-type material composed of at least 10 repeat units from the reaction between decaborane and adiponitrile (NC(CH2)4CN). Also reported,9 is the inclusion of flexible siloxanes and ether linkages into a diamine, and of their subsequent reaction with decaborane to give adduct polymers (see 2, 3). 

Some cycloaddition reactions of 4 are summarized in Scheme 1. This shows that silylene 4 undergoes reactions with nitriles [14], phosphaalkynes [15], silyl azides [16], diazabutadienes [17], 2,2 -bipyridyl and its derivatives [18, 19], a-ketoimines [19], and pyridine-2-aldimines [19]. 

Another example of the remarkable reactivity of Mg actuated by our procedure is its reaction with nitriles. In this respect, the Mg resembles an alkali metal more than an alkaline earth. Benzonitrile reacts with Mg overnight, in refluxing DME, to give 2,4,6-triphenyl-l,3,5-triazine and 2,4,5-triphenylimidazole in 26 and 27% yield, respectively, based on magnesium. Jhe imidazole was shown to arise, at least in part, from the action of Mg on the triazine. The trimerization of aromatic nitriles to give symmetrical triazines is not unknown, but generally the reactions are... 

S-Nucleophiles are very reactive in 1,3-addition reactions with nitrile oxides. A series of a-glucosinolates 27 (R = CR1=NOH R1 =Ph, CH2PI1, CH2CH2PI1, ( )-CH=CHPh, 3-indolylmethyl) was prepared by addition reactions of thiol 27 (R = H) with nitrile oxides (123). The indolyl-substituted glucosinolate was then converted to a-glucobrassicin 28. 

Heterocycles Both non-aromatic unsaturated heterocycles and heteroaromatic compounds are able to play the role of ethene dipolarophiles in reactions with nitrile oxides. 1,3-Dipolar cycloadditions of various unsaturated oxygen heterocycles are well documented. Thus, 2-furonitrile oxide and its 5-substituted derivatives give isoxazoline adducts, for example, 90, with 2,3- and 2,5-dihydro-furan, 2,3-dihydropyran, l,3-dioxep-5-ene, its 2-methyl- and 2-phenyl-substituted derivatives, 5,6-bis(methoxycarbonyl)-7-oxabicyclo[2.2.1]hept-2-ene, and 1,4-epoxy-l,4-dihydronaphthalene. Regio- and endo-exo stereoselectivities have also been determined (259). 

Dipolar cycloaddition of 2,4-(trimethylsilyl)- and 2,4-(trimethylgermyl)-substituted thiophene-1,1-dioxides as well as silylated 2,2 -bithiophene-1,1-dioxides was investigated. It was shown that only the C(4)=C(5) double bond of 2,4-disubstituted thiophene-1,1-dioxides interacts with acetonitrile oxide to give thienoisoxazoline dioxides. Bithiophene derivatives were inactive or their reaction with nitrile oxide was accompanied by desilylation. Cycloaddition of benzonitrile oxide with all mentioned sulfones did not occur. The molecular structure of 3a-methyl-5.6a-bis(trimethylgermyl)-3a,6a-dihydrothieno 2.3-c/ isoxazole 4,4-dioxide was established by X-ray diffraction (263). ... 

I.3.4.2. Intermolecular Cycloaddition at C=X or X=Y Bonds Cycloaddition reactions of nitrile oxides to double bonds containing heteroatoms are well documented. In particular, there are several reviews concerning problems both of general (289) and individual aspects. They cover reactions of nitrile oxides with cumulene structures (290), stereo- and regiocontrol of 1,3-dipolar cycloadditions of imines and nitrile oxides by metal ions (291), cycloaddition reactions of o-benzoquinones (292, 293) and aromatic seleno aldehydes as dipolarophiles in reactions with nitrile oxides (294). 

Cyclic imidate esters, 2-ethoxypyrrolin-5-one and 2-ethoxy-1II -indol-3-one, undergo 1,3-dipolar cycloaddition reactions with nitrile oxides, the reaction site being at the pyrroline C=N bond (317). Rigid and sterically congested pyrroline spiro compounds 148 demonstrate complete diastereofacial selection in site and regiospecific cycloaddition reactions with nitrile oxides to give products 149 (318). 

Iodoacetylene (prepared in situ from ethynylmagnesium bromide or tributyl (ethynyl)tin with iodine) was used as a dipolarophile in the 1,3-dipolar cycloaddition reactions with nitrile oxides to produce 2-(5-iodoisoxazol-3-yl)pyridine and 3-(4-fluorophenyl)-5-iodoisoxazole in good yield (70%-90%). Subsequently,... 

Syntheses of l-aryl-3,3,3-trilluoro-l-propynes and their reactions with nitrile oxides to give 3,5-diaryl-4-tri(luoromethylisoxazoles have been carried out. In particular, l-(4-chlorophenyl)-3,3,3-trilluoro-l-propyne, on reaction with 4-chlorobenzohydroximoyl chloride in the presence of Et3N in PhMe, give a 45% mixture of 211 (R = R1 = 4-CIC6H4) and the regioisomer 212 in the ratio of 97 3, respectively (370). 

The carbon-nitrogen triple bond of aryl thiocyanates acts as a dipolarophile in 1,3-dipolar cycloadditions. Reactions with nitrile oxides yield 5-arylthio-1,2,4-oxadiazoles 227 (X = O Y = S). Aryl selenocyanates behave similarly forming 5-arylseleno-l,2,4-oxadiazoles 227 (X = 0 Y = Se). Reactions of 5-aryl-... 

In the case of primary carbocation, reaction with nitrile oxide gives a mixture of two regioisomeric oximes (Scheme 1.41). Probably, this is a result of the attack of the nitrile oxide - BF3 complex on neutral 3-chloromethylanisole. 

Unsaturations of hydroxy-containing compounds are reduced on reaction with nitrile oxides such as tetramethyl terephthalonitrile N,N -dioxide (506) or 1,3,5-triethylbenzene-2,6-dicarbonitrile oxide (507). The reaction of a nitrile oxide with terminal unsaturation, associated with the preparation of a poly-ol from propylene oxide, reduces the mono-ol content of the poly-ol composition. Thus, stirring a solution of an ethylene oxide-propylene oxide copolymer with an OH content of 2.39% and vinyl unsaturation of 3.58% in THF with l,3,5-triethylbenzene-2,6-dicarbonitrile oxide for 1 min results in an effective removal of the terminal unsaturation. 

Although monodentate isocyanide-tantalum complexes are available by alternative routes,204 the majority of studies are concerned with the resultant 2-imines. Conversely, similar reactions with nitriles give monodentate imine moieties, which can undergo reactions while remaining attached to the metal.195,203-209... 

The radical cations (47) produced by T oxidation of aryl aldehyde hydrazones acted as 1,3-dipoles in reaction with nitriles to form, after a second T oxidation, 1,2,4-triazoles (Scheme 4) (85TL5655). 

---