Crystalline Silaspiropentane and Its Rearrangement to Silacyclobutane

Area of Science:

• Organosilicon Chemistry
• Organic Synthesis
• Reaction Mechanisms

Background:

• Silaspiropentanes are novel silicon-containing compounds.
• Understanding their synthesis and reactivity is crucial for advancing organosilicon chemistry.

Purpose of the Study:

• To synthesize and crystallographically characterize the first silaspiropentane.
• To investigate the thermal rearrangement of silaspiropentane.
• To compare the reactivity of silaspiropentane with its carbon analogue, spiropentane.

Main Methods:

• Synthesis of silaspiropentane via addition of a silylene compound to methylidene cyclopropane.
• Isolation and crystallographic characterization of silaspiropentane.
• Kinetic studies of the thermal rearrangement.
• Comparison with reactions involving cyclic alkyl amino carbene (cAAC) and methylidene cyclopropane.
• Density Functional Theory (DFT) calculations to elucidate reaction mechanisms.

Main Results:

• The first crystallographically characterized silaspiropentane was successfully synthesized.
• Silaspiropentane undergoes thermal rearrangement to methylene silacyclobutane via a first-order reaction.
• Spiropentane, derived from cAAC, did not rearrange, but aryl-substituted analogues formed E-stereoisomer methylene cyclobutanes.
• DFT calculations revealed distinct transition state geometries for spiropentane and silaspiropentane rearrangements, supporting a concerted mechanism.

Conclusions:

• The successful synthesis and characterization of silaspiropentane open new avenues in organosilicon chemistry.
• The observed thermal rearrangement provides valuable kinetic and mechanistic data.
• Comparative studies highlight the influence of silicon on the reactivity and rearrangement pathways compared to carbon analogues.