Substituted imines

A thermal ring opening reaction of an imine-substituted cyclopropene led to a mixture of 2,3,4-trisubstituted and 3,4,5-trisubstituted pyrroles <06TL5793>. 

A RhCp complex (S,S)-6 (Cp =pentamethylcyclopentadienyl), which is iso-lobal with Ru(rj6-arene) complex (S,S)-5 (Scheme 13), effected the transfer hydrogenation of a cyclic imine substituted by an isopropyl group with an S/C of 200 in the presence of a 5 2 mixture of formic acid and triethylamine to give the R amine in 99% ee (Scheme 13) [31]. When the reaction was performed with an S/C of 1,000, the optical yield decreased to 93%. The methyl imine was reduced with a 91% optical yield. Reduction of a cyclic sulfonimide resulted in the R sul-tam in 81% ee. 

Although thermodynamically stable in aqueous solution, complex 1 nonetheless readily underwent covalent imine substitution in the presence of sulfanilic acid to form 2 (Scheme 1.2). 

Pseudotetrahedral complexes such as 17 (Scheme 1.17) were observed to possess a particularly rich substitution chemistry [37]. Complex 17 reacted cleanly with o-phenylenediammonium to give the covalent substitution product 18 shown in Scheme 1.17. This imine substitution was driven by the same pk, effect employed in the l-to-2 transformation of Scheme 1.2. In addition, 17 reacted cleanly with copper bis(biquinoline) complex 10 to give the coordinative substitution product 20. This ligand exchange appears to have been sterically driven the substitution of one of the encumbering di(imine) ligands for a less bulky biquinoline provided the driving force for this reaction [45],... 

Applications of the Vilsmeier-type reaction to the synthesis of a variety of imine-substituted indoles have been reported. The scope appears to be very wide and further examples will undoubtedly be forthcoming. Perhaps the most important development is the use of triflic anhydride in combination with amides to generate highly reactive imino-triflate reagents in situ, and this general area of reagent modification is also likely to develop. 

Di(p-tolyl)-1,10-phenanthroline 14 is synthesized in 70% yield from 1,10-phenanthroline 3 (1 equiv) and 4-lithiotoluene 13 (5 equiv), after hydrolysis, oxidation with Mn02 and recrystallization (Scheme 9.11). This reaction, detailed in Protocol 9, follows a literature procedure to make various poly-imines substituted by alkyl or aryl groups a to the nitrogen atoms.20... 

An enantioselective Friedel-Crafts alkylation of pyrroles with /V-acylimincs has been reported <070L4065>. The reactions were run in the presence of chiral phosphoric acids. A novel C-H bond activation procedure was developed for the preparation of heteroarylamides including pyrrole-3-carboxamides <07CL872>. The reactions involved imine-substituted pyrroles, isocyanate electrophiles, and a rhenium catalyst. 

By the Fp-assisted cyclization of y,<5-unsaturated imines, substituted carbapenams were prepared, with overall low yield and low diastereoselectivity34,35. 

Models used to explain and predict diastereofacial selectivity in related carbonyl addition reactions (Figure 7) can be utilized to predict similar selectivity in allyl organometallic-aldimine condensations. As a consequence of the type of imine substitution, addition reactions can be divided into two types (i)... 

As reported by Mauze, the reaction of gem-chloro(methyl)allyllithium (17) with aldimines and ke-timines (18) is an efficient method for the synthesis of 2-vinylaziridines (20 Scheme 3). The aziridine ring is formed by intramolecular Sn2 chloride displacement via the intermediate lithium amide (19). The products are formed as diastereomeric mixtures, as indicated by NMR, and ratios of diastereomers vary depending on the imine substitution. Yields tend to be higher with more accessible linear and branched... 

Additives can also be used to improve the hydrolytic stability of polyester polyurethanes. Glycol-cured materials are reported to be stabilized with cyclic imines. Substituted ureas or thioureas ethylene-diaminetetraacetic acid-derived chelating agents oxycarbonyl isocyanates epoxies carbodiimides, alone " or in combination with silica silanes " substituted phthalimides and an undisclosed combination of additives have all been cited as stabilizers for polyester polyurethanes. 

One would expect that the aldimine would add to the less-hindered face of the ketene. Computational studies support this conelusion, showing that exo attack leads to lower energy transition states. Further proof that exo attack is the exclusive pathway of aldimine addition has been developed using cyclic Z-imines substituted with various electron-donating and electron-withdrawing substituents. ... 

Quinone imine-substituted ( n -cyclohexa-l,3-diene)iron complexes are obtained by oxidation of the corresponding p-anisidine precursors with manganese dioxide (Scheme 4—133). Treatment of the former species with very active manganese dioxide triggers an oxidative cyclization to afford iron-coordinated 4b,8a-dihydrocarbazol-3-Demetalation with trimethylamine N-oxide leads via concomitant... 

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