Carbene Additions to Aldehydes and Imines

Diazo compounds react with aldehydes and ketones to give homologated carbonyl compounds and epoxides. Lewis acids accelerate these processes, and in some cases direct the reactions to single products. frara-Epoxides result from aldehydes and ethyldiazoacetates in the presence of MeReOs (although this can occur via a metal carbene pathway rather than a Lewis acid mechanism) [139], whereas 

The same iron complex also catalyzes the reaction of imines and diazo compounds to give d -aziridines (Sch. 31) [142]. 

Doubly activated imines undergo intramolecular electrophilic cyclization reactions in the presence of Lewis acids and this provides an efficient route to annulated pyrrolidine, piperidine and azepine lactones (Sch. 32) [143]. TMSOTf and GaCls give different product ratios and yields. 

2-additions of nucleophiles to isoquinolines coordinated to a chiral rhenium Lewis acid are reported to be highly diastereoselective. Subsequent reaction of the enamine complex with reactive electrophiles then reduction affords 1,4-dialkyl tetra-hydroisoquinolines. The Re Lewis acid can be recycled (Sch. 33) [144]. 

The complexes (5,5)-(Phebox)Pt(OTf) and [(5,5)-(Phebox)Pt(H20)](BF4) react with A -phenylbenzaldimine to afford the corresponding chiral aldimine complexes. Addition of organolithium reagents gives, after work-up, the corresponding enantio-merically enriched amines (Sch. 34) [145], 

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