Imines nitriles

Lithium aluminum hydride (LiAlH4) is the most powerful of the hydride reagents. It reduces acid chlorides, esters, lactones, acids, anhydrides, aldehydes, ketones and epoxides to alcohols amides, nitriles, imines and oximes to amines primary and secondary alkyl halides and toluenesulfonates to... 

In a manner analogous to classic nitrile iinines, the additions of trifluoro-methylacetonitrile phenylimine occur regiospecifically with activated terminal alkenes but less selectively with alkynes [39], The nitnle imine reacts with both dimethyl fumarate and dimethyl maleate m moderate yields to give exclusively the trans product, presumably via epimenzation of the labile H at position 4 [40] (equation 42) The nitrile imine exhibits exo selectivities in its reactions with norbornene and norbornadiene, which are similar to those seen for the nitrile oxide [37], and even greater reactivity with enolates than that of the nitnle oxide [38, 41], Reactions of trifluoroacetomtrile phenyl imine with isocyanates, isothiocyanates, and carbodiimides are also reported [42]... 

Likewise, trifluoromethyl-substituted nitrile imines [172] and nitnle oxides [173,174, 7 75] have been used to synthesize tnfluoromethyl substituted five-membered ring systems of the pyrazole, isomzole, isoxazohne, and 1,2,4-oxadiazole... 

Intramolecular reactions of nitrile imines as a fruitful source of heterocycles 98H(47)541. 

Another 1,7-dipolar cyclization leading to 1,2-benzodiazepines, but with the difference that a C-C bond is formed, is the ring closure of the nitrile imines 15 to give 17 by a [1,5]-sigmatropic shift of hydrogen in the intermediates 16. The nitrile imines are generated from the (2-vinylphenyl)hydrazonoyl chlorides 14."8 120... 

Methyl-17/-l,5-benzodiazepin-2(37/)-one undergoes addition to nitrile imines at the 4,5-bond, e.g. formation of 33.-10 1... 

Bcnzotriazepincs 10 are produced in the reaction of nitrile imines 9 with 2-phenyl-benzazctc.379... 

Bernsteinaldehydsaure 526, 529 -chlorid 184 -diathylacetal-nitril 363 -nitril 604 -nitril-imin 112... 

Diazoalkane" Nitrous oxide Nitrile imine Nitrile ylid Nitrile oxide ... 

Photoelimination of nitrogen from the tetrazole 429 results in the formation of the dihydropyrazole 430, presumably via intramolecular addition of the photochemically generated nitrile imine 431.358 Other examples of this type of behavior have been reported.359... 

The photoelimination of carbon dioxide from esters and lactones is a process that has been the subject of detailed investigations. Discussion here is limited to nitrogen containing systems. 3,4-Diphenylsydnone (464), on irradiation in benzene, is converted via the nitrile imine 465 into 2,4,5-triphenyl-1,2,3-triazole (466)388 initial bond formation between N-2 and C-4 followed by loss of carbon dioxide to give the diazirine 467 is proposed to account for the formation of the nitrile imine. Nitrile imines generated in this way have been trapped with alkenes and alkynes to give pyrazoles389... 

An alternative strategy for generating 4,5-dihydropyrazoles is to perform 1,3-dipo-lar cydoaddition reactions of nitrile imines and alkenes. Langa and coworkers have... 

Spiro[3H-indole-3,5(4.H)-(l,2,4)triazoline]-2-one derivatives 204 have been obtained using microwave irradiation in the reaction between imines of isatin 203 and nitrile imines generated in situ from the corresponding hydrazonyl chlorides 199 (Scheme 9.63). The yields are in the range 85-95% and the reaction is complete within 5 min [110]. Similar reactions performed under thermal conditions were complete in 6-10 h and yields decreased to 20-30%. However, when the reaction was performed at ambient temperature, the products were obtained in excellent yields but only after a prolonged reaction time (30 h). 

The formation of several pyrazolylpyrazolino[60]fullerene adducts (208a-c) from nitrile imines have been described (Scheme 9.64) [111]. The nitrile imines are generated in situ from the corresponding hydrazone 205 and NBS in the presence of Et3N... 

Highly functionalized tetraaryl-4,5-dihydro-l,2,4-triazoles 118a-y have been prepared on a soluble polymer support (PEG4000) from the cycloaddition of diarylimines with a nitrile imine, prepared in situ from the arylhydra-zone 119. The triazole products are highly fluorescent and several have reasonable fluorescence quantum yields (Scheme 8 and Table 19) <2005S3535>. 

The sydnone and sydnonimine ring systems are stable in acid solution at room temperature but are rapidly hydrolyzed in basic media <1984CHEC(6)365>. 3,4-Diarylsydnones 67 lose carbon monoxide on photolysis giving nitrile imines 68 that can be intercepted by dipolarophiles (Equation 1) <2004TL9057>. 

Some new spirothiadiazolepyrazolo[l, 4-e/][1,5] benzodiazepines have been reported by Rakilo et al. They are prepared by a regioselective 1,3-dipolar cycloaddition of a nitrile imine with pyrazolo[l,5,4-e/][ 1,5]benzodiazepine-thione <00H(53)571>. 

Burk et al. showed the enantioselective hydrogenation of a broad range of N-acylhydrazones 146 to occur readily with [Et-DuPhos Rh(COD)]OTf [14]. The reaction was found to be extremely chemoselective, with little or no reduction of alkenes, alkynes, ketones, aldehydes, esters, nitriles, imines, carbon-halogen, or nitro groups occurring. Excellent enantioselectivities were achieved (88-97% ee) at reasonable rates (TOF up to 500 h ) under very mild conditions (4 bar H2, 20°C). The products from these reactions could be easily converted into chiral amines or a-amino acids by cleavage of the N-N bond with samarium diiodide. 

Less frequently applied are [3 + 2] and [2 + 2] cycloadditions of oxygen-substituted allenes [102-104], Battioni et al. described only a limited number of [3 + 2] cycloadditions of phenyloxy- and methoxyallene with diphenyldiazomethane (157) and the nitrile imine derived from diphenylhydrazonoyl chloride (159) (Scheme 8.40) [102], Both 1,3-dipoles exclusively attack the terminal C=C bond, furnishing cycloadducts 158 and 160. Padwa et al. reported [3 + 2] cycloadditions of methoxyallene 145 with two nitrones which afforded isoxazolidines in low yield [103]. 

Simultaneous formation of a two-ring system from acyclic intermediates has also been reported. For example, the reaction of carbonyl-stabilized sulfur ylides with nitrile imines afforded furo[3,2-c]pyrazoles (69TL853). 

Cycloalkanone oximes 157 reacted with nitrile imines forming spirotriazolines 158 in 48-61% yields (equation 69) . 

Dihydrodiazepines have been shown to undergo regioselective cycloaddition reactions with nitrile oxides or nitrile imines (88MI1 89JHC1619). 

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