Diamines imines, cyclic

Aromatic diamines, isothiosemicarbazides, cyclic and aliphatic diamines, 1,2-bis(aminooxy)ethane etc. can all serve as closing agents, providing the formation of softer metal-binding sites by incorporation of imine nitrogens into the macrocycle formed. 

In addition to their antiknock properties, organic lead compounds possess bactericidal properties and motor fuels with lead are known to inhibit bacterial growth during storage in contact with water. With the disappearance of lead-based compounds, it is necessary to incorporate biocides from the cyclic imine family, (piperidine, pyrrolidine, hexamethyleneimine), alkylpropylene diamines or imidazolines (Figure 9.2). 

Ru-diphosphine-diamine complexes developed originally by Noyori for the hydrogenation of aryl ketones are also suitable for the hydrogenation of imines. The best results are obtained for N-aryl imines where a Ru-duphos-diamine complex achieved up to 94% ee, albeit with relatively low activity and productivity (entry 3.7) (for data relating to cyclic imines, see Table 34.5). 

Cyclic imines 8 and 9 are intermediates or models of biologically active compounds and can be reduced with ee-values of 88 to 96% using Ti-ebthi, Ir-bcpm or Ir-binap in the presence of additives (entries 5.7, 5.9), as well as with the transfer hydrogenation catalyst Ru-dpenTs (entries 5.8, 5.10-5.12). As pointed out earlier, Ru-diphosphine-diamine complexes are also effective for imines, and the best results for 7 and 8a were 88% and 79% ee, respectively [36]. Azirines 10 are unusual substrates which could be transfer-hydrogenated with a catalyst prepared in situ from [RuCl2(p-cymene)]2 and amino alcohol L12, with ee-values of 44 to 78% and respectable TOFs of up to 3000 (entry 5.13). 

A water-soluble, recyclable ruthenium(II) complex including a chiral diamine ligand has been used for asymmetric transfer hydrogenation of cyclic imines and iminiums in water, with yields and ee up to 99%.49... 

Scheme 5.17).40 A three-step reduction-deprotection protocol liberated the aratz -vicinal diamine 21. A six-membered cyclic transition-state structure was proposed to account for the anti selectivity after a two-electron reduction of the nitrone. The chiral A-tert-butylsulfinyl group directs the attack of the carban-ion to the Sz-face of the C=N double bond of the imine. 

In NC(CH2)nCN Conversion (%) Aminonitrile Cyclic Imine Diamine Dimeric product... 

Preparative Methods (i) preparation of racemic DPEN and its optical resolution Reaction of benzil and cyclohexanone in the presence of ammonium acetate and acetic acid at reflux temperature gives a cyclic bis-imine (1) (eq 1). Stereoselective reduction of the bis-imine with lithium in THF-liquid ammonia at —78 °C followed by addition of ethanol, then hydrolysis with hydrochloric acid and neutralization with sodium hydroxide produces the racemic diamine (2). Recrystallization of the l-tartaric acid salt from a 1 1 water-ethanol mixture followed by neutralization with sodium hydroxide, recrystallization from hexane results in (5,5)-DPEN (3) as colorless crystals. 

Either antipode of bromoborane 332 can be prepared in a six-step sequence from benzil (330, Scheme 11-19) [127, 254, 258J. Reaction of benzil with cyclohexanone in the presence of ammonium acetate and acetic acid generates a cyclic bis-imine which is subsequently reduced with lithium in ammonia. The resulting racemic fra .s-imidazolidine is subsequently hydrolyzed to the diamine 331. Resolution of 331 is accomplished by crystallization with either antipode of tartaric acid. The enantiomerically enriched stein ligand 331 is then sulfonylated and condensed with boron tribromide, giving the chiral bromoborane 332. Transmetalla-tion of allyltri-n-butylstannane with bromoborane (R,/ )-332 then affords the allyl-boron reagent (R,/ )-198. 

In seeking an efficient, economic, and scaleable route to the new potent nonnucleoside HIV-1 reverse transcriptase inhibitor 16 (L-738,372) [2a], process chemists at the Merck Research Laboratories have significantly contributed to the field of asymmetric alkylation of imines. Huffman and co-workers have reported a very efficient asymmetric route to 16 via the addition of a lithium acetylide to the cyclic N-acylketimine 14 in the presence of the lithium alkoxide of the alkaloid quinine as a stoichiometric chiral additive (Scheme 9) [31aj the previous route to the inhibitor 16 included a resolution step [31bj. Whereas other types of chiral additives were screened (e.g., diamines, diethers), only P-ami-no alkoxides were enantioselective. The search for readily available amino alcohols was dictated by the necessity of developing a practical process. The commer-... 

As the name suggests, diamine oxidase catalyzes the oxidative deamination of diamines. Preferably a,co-diamines such as putrescine (1,4-diaminobutane) or cadaverine (1,5-diaminopentane) (the names already suggest their smell), but also various derivatives are readily converted. Quite often cyclic imines are obtained via internal nucleophilic attack by the unreacted amino function (Fig. 16.7-16) l38 40l. 

Bergman and Brynolf (1989) reported an interesting synthesis of a cyclic bis Schiff base. They treated a linear bis Schiff base containing two chloro-or fluorophenyl units with a diamine to form the symmetrical cyclic bis Schiff base similar to that shown above. It is evident that one of the imine carbon... 

Synthesis of 1,6-diaminohexane from the corresponding diol and ammonia is complicated by cyclization either via the amino alcohol intermediate or by disproportionation of the diamine (Scheme 8) [24], The best selectivity was achieved with Raney Ni in dioxane - 67 % for the diamine and 33 % for hexamethylenei-mine at 58% conversion. The selectivity for 1,6-diaminohexane could be increased to nearly 100 % by partial recycling of the cyclic imine, i. e. no additional imine was formed in the equilibrium reaction. 

Hexahydro-l(//)-azepine may be prepared by the Cu/Al202-catalyzed cyclization of 6-amino-l-hexanol <89AC107>, and hexamethylene diamine is converted to the cyclic imine by pea seedling diamine oxidase <90TL6907>. 

Magnesium silicate Cyclic imines from diamines... 

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