Raney nickel aziridines

The azidohydrins obtained by azide ion opening of epoxides, except for those possessing a tertiary hydroxy group, can be readily converted to azido mesylates on treatment with pyridine/methanesulfonyl chloride. Reduction and subsequent aziridine formation results upon reaction with hydrazine/ Raney nickel, lithium aluminum hydride, or sodium borohydride/cobalt(II)... 

Aziridines, like oxiranes, undergo hydrogenolysis easily with or without inversion of configuration, depending on the catalyst, reaction parameters, and various additives 65aJ08). For example, hydrogenolysis of 2-methyl-2-phenylaziridine in ethanol occurs mainly with inversion over palladium but with retention over platinum, Raney nickel, or Raney cobalt. Benzene solvent or alkali favor retention over palladium as well. 

Sugar azides are also important starting-materials for the synthesis of epimino sugars an azido group adjacent to a p-tolylsulfonyloxy group, as in 6 or 8, may be simultaneously reduced and cyclized with Raney nickel to form an aziridine ring, as in 7, especially if the two groups are in the frans-diaxial position.19 22... 

Ricart et al.231,236 reported that hydrogenation of l-[/V-(5-hydroxypentyl)-3-aminopropyl]aziridine over Raney nickel gave a mixture of the unsubstituted and the 1-ethyl-substituted perhydropyrido[l,2-n]pyrimidine. The former was also obtained by reacting 5-hydroxypentylamine and acrylonitrile, followed by hydrogenation over Raney nickel. 

Catalyt c hydrogenation (palladium or Raney nickel catalyst) surprisingly results in reduction of the carbon-nitrogen single bond rather than the double bond.4,12,40 The imines, or possibly enamines, are usually not isolated and their existence has only been inferred in most instances. Harvey and Ratts have shown that this reaction with azirine (165) does not proceed first to the aziridine which is then reduced to 166, since aziridine (167) is inert to hydrogen and palladium on carbon.40... 

All types of electrophiles have been used with 2-lithio-l,3-dithiane derivatives, including alkyl halides, sulfonates, sulfates, allylic alcohols, arene-metal complexes, epoxides, aziridines, carbonyl compounds, imines, Michael-acceptors, carbon dioxide, acyl chlorides, esters and lactones, amides, nitriles, isocyanates, disulfides and chlorotrialkylsilanes or stannanes. The final deprotection of the dithioacetal moiety can be carried out by means of different types of reagents in order to regenerate the carbonyl group by heavy metal coordination, alkylation and oxidation184 or it can be reduced to a methylene group with Raney-nickel, sodium or LiAIII4. 

Ponsold synthesized steroid aziridines by reduction of mesylate esters of vicinti aado alcohols with hydrazine hydrate and Raney nickel. 

Two frans-diaxial azido compounds (252 and 254) have been converted into aziridines by using Raney nickel in hydrazine, in reactions that can... 

Aziridin-1-yl-1,3,5-triazines, in the presence of acidic catalysts, can be transformed into dihydroimidazofl, 2-a]-l, 3,5-triazines. When the tris-aziridinyl derivative 1 is heated to reflux in acetonitrile for 1.5 hours in the presence of triethylamine hydrochloride, the tetracyclic hexahydrotriimidazo[l,3,5]triazine 2 is formed in about 77% yield.31 Noteworthy is the fact that the same conversion can also be achieved under reducing conditions by performing the reaction in dioxane at 100°C in the presence of a Raney nickel catalyst under hydrogen pressure.31... 

---