Abstract

Easy as 1,2,3: Reaction of methyl carbamate, triethyl orthoformate, and readily available alkenes provides a highly practical preparation of protected aminocyclopropanes. The reaction proceeds with preferential cis addition to alkenes, and cleavage of the methyl carbamate gives the free aminocyclopropanes as their HI salts.

Highlights

  • The aminocyclopropane unit can be found in a wide variety of biologically active natural products and pharmaceuticals,[1] and its inherent reactivity can be harnessed in synthetically useful ring-opening reactions.[2]

  • We have previously shown that functionalized organozinc carbenoids can be generated from carbonyl compounds or acetals by reductive deoxygenation with zinc in the presence of Me3SiCl,[12] and this strategy can be extended to the

  • All efforts to prepare and isolate the desired precursor 1 were uniformly unsuccessful,[18] with the NMR spectra of the complex reaction mixtures indicating the presence, inter alia, of the N,Nbis(diethoxymethyl) derivative and the imino ether. Undeterred by these observations and in spite of the fact that competing alkoxycyclopropanation[13] or further reaction of the product leading to double cyclopropanation could take place, we decided to explore an even more adventurous onepot sequence involving in situ formation of the carbenoid 2

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Summary

Synthetic Methods

All efforts to prepare and isolate the desired precursor 1 were uniformly unsuccessful,[18] with the NMR spectra of the complex reaction mixtures indicating the presence, inter alia, of the N,Nbis(diethoxymethyl) derivative and the imino ether Undeterred by these observations and in spite of the fact that competing alkoxycyclopropanation[13] or further reaction of the product leading to double cyclopropanation could take place, we decided to explore an even more adventurous onepot sequence involving in situ formation of the carbenoid 2. The result of applying the optimal reaction conditions to direct carbamatocyclopropanation of 6 using MeOCONH2 and (EtO)3CH afforded the cyclopropane 10 in 78 % yield (Scheme 3), effectively mirroring those described above for 9, save for the fact that the reactions were even faster at room temperature With this mild and convenient method in hand, the scope of the reaction was explored with respect to the alkene component

Entry Carbenoid Precursor
Experimental Section

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