Synthesis of Spiro[2.2]pentanes and Spiro[2.3]hexanes Employing the Me₃Al/CH₂I₂ Reagent

Abstract

Substituted alkylidenecyclopropanes reacted with 5 equivalents each of Me3Al and CH2I2 at room temperature in hexane to give 1‐mono‐ and 1,1‐disubstituted spiro[2.2]pentanes in high yields. Surprisingly, the same reaction with substituted alkylidenecyclopropanes in CH2Cl2 afforded exclusively 1,1‐disubstituted spiro[2.3]hexanes. The transformation of 1,1‐diphenylspiro[2.2]pentane into 1,1‐diphenylspiro[2.3]hexane was studied with the use of CD2I2 and a plausible mechanism was suggested. The reaction of substituted alkylidenecyclobutanes with the Me3Al/CH2I2 reagent in CH2Cl2 gave only 1,1‐disubstituted spiro[2.3]hexanes.

Activation and Functionalization of C–C σ-Bonds of Alkylidene Cyclopropanes at Main Group Centers

“…Compounds 2a-d were characterised by 1 H and 13 C NMR. These are known compounds and data match the literature values (2a-2b, 3 2c, 4 , 2d 5 ). All compounds were stored in the glovebox for further use.…”

Synthesis of Spirocyclic Cyclopropyl Glycosyl-1-phosphate Analogues

“…When the reaction was carried out in dichloromethane in the presence of 0.2 equiv of diethylzinc, the desired products were not observed (Table , entry 1) even if TFA was added (Table , entry 2) . Neither the use of Zn–Cu nor AlCl 3 as catalyst produced the desired products (Table , entries 3 and 4). , This lack of reactivity likely originates from the phosphonyl group that both hinders the enol ether and strongly modifies its electronic distribution as compared to classical methylene exo -glycals or endo -glycals. Harsher cyclopropanation conditions based on the methodology developed by Tang et al were thus explored and led to the dibenzyloxyphosphoryl spirocyclopropanes 9a and 10a in moderate yields when DCE, and not DCM, was used as the solvent (Table , entries 5 and 6) …”