Imines seven-membered cyclic

Organolanthanides are efficient catalyst precursors for the regioselective (>95%) IH of primary aminoalkynes, forming five-, six-, and seven-membered cyclic imines via Exo-Dig processes (Eq. 4.86) [303, 304]. 

Recently, Olsson and coworkers have reported a cross-coupling reaction between seven-membered cyclic imidoyl chlorides and alkyl Grignard reagents (Scheme 36). The corresponding substimted imines, which are very difficult to prepare otherwise, are synthesized in good to excellent yields. 

Cycloaddition reactions were also carried out using l,2-bis(trifluoromethyl)-fumaronitrile (137,138,191,192). Seven-membered cyclic ketene imines (186-188) could actually be isolated in good yields from the reactions with 69,... 

With adiponitrile, an open-chain dinitrile, however, such cyclization leading to a seven-membered cyclic imine occurs to a much lesser extent (see, e.g., eq. 7.25). The hydrogenative cyclizations have been utilized for the synthesis of pyrrolidine and piperidine derivatives from 1,2- and 1,3-dicyano compounds.118,119... 

Selected examples of intramolecular aminoalkyne hydroamination catalyzed by rare-earth metal complexes (see Figs.8, 16, and 18) are shown in Schemed and Tables. Formation of five-, six-, and seven-membered cyclic imines has been achieved in excellent yields. 

An example of the use of the tandem Staudinger/aza-Wittig reaction to form a seven-membered ring comes from the total synthesis of the alkaloid (-)-stemospironine (76).34 In this example, azidoaldehyde 74 was treated with triphenylphosphine to form a seven-membered cyclic imine which was then followed by an in situ sodium borohydride reduction to afford 75. Treatment of the resulting amine with iodine initiated the formation of the pyrrolidino butyrolactone system of the final target. 

However, it was observed [ 103] that reaction of titanium(IV) enolates derived from homophthahc anhydride and five-, six- and seven-membered cyclic imines also yield trara-adducts instead of the expected cu-isomers (Scheme 2.9). 

A rather small Vff coupling of 2.6 Hz only has been observed by Langhals et al in the spectrum of (6SR,yRS) diastereoisomer obtained upon base-catalyzed dimerization of the strained seven-membered cyclic ketene imine (see Figure 5). 

A method for the asymmetric hydrogenation of seven-membered cyclic imines of benzodiazepinones and benzodiazepines has recently been published. The chiral cyclic amines generated from these reactions make up the cores of many natural products and clinical drugs. Iridium-bisphosphine catalyst systems were investigated and found to give promising enantios-electivities which could be improved upon addition of morpholine tri-fluoroacetate. The optimum conditions, applied to model compound 50, are shown in Scheme 14.19, giving 51 in excellent enantioselectivity and complete conversion. 

Hydrogenation of seven-membered cyclic imines of benzodiazepinones and benzodiazepines has been promoted by an Ir-diphosphine complex with up to 96% ee. ... 

The catalyst-free 5-1-1-cycloaddition reaction between C, A(-cyclic A -acyl azome-thine imines (134) with isocyanides (135) formed imin-l,3,4-oxadiazin-6-one derivatives (136) in high to excellent yields (99%) under mild conditions (Scheme 42). The cobalt-mediated / -pentadienyl (137)/alkyne (138) 5-1-2-cycloaddition reaction yielded /, -cycloheptadienyl complexes (139) under kinetic control. The initial cycloadducts are isomerized to the final >/ -cycloheptadienyl complexes (140) (Scheme 43). The Ru(I)-catalysed intra- and intermolecular 5 4- 2-cycloaddition reactions of 3-acyloxy-l,4-enynes and alkynes produced adducts with highly functionalized seven-membered rings. The reaction sequence includes a 1,2-acyloxy migration. The catalyst-free 5 4- 2-cycloaddition reaction of 2-vinylaziridines with sulfonyl isocyanates in CH2CI2 yielded seven-membered cyclic ureas in high yields (up to 90%). ... 

With five- (or four)-membered-ring cyclic imides (Scheme 16) 57 initially gives isolable eight- (or seven)-membered ring intermediates (58, 60, and 62), which can be converted readily to products 59,61, and 63. The key step appears to be transannular attack of the imine nitrogen of the intermediate on the amide carbonyl. This is followed by attack of a nucleophile and ring opening via a number of possible pathways. ... 

Under strictly anhydrous conditions, the iminophosphorane intermediate that is formed as a result of the Staudinger reaction can react with aldehydes and ketones in an intermolecular fashion (as in the synthesis of imine 36 described above) or intramolecularly with a variety of carbonyl containing functional groups to afford a host of products. Nitrogen containing ring systems such as cyclic imines (44) represent just one of the many products one can prepare and the reaction is particularly well suited for the facile synthesis of five, six, and seven-membered rings. In addition to aldehydes and ketones, carboxylic acids, esters, thio-esters, and amides can also react in an intramolecular fashion to trap an iminophosphorane to afford a variety of heterocycles. Examples from the current literature are described in Section 2.5.5. 

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