Ring-opening mechanism of disilacyclopropylidenoids and trisilacyclopropylidenoid: A theoretical study

Substituent effects on the ring-opening mechanism ofgem-dibromospiropentanes to related allenes: a theoretical study

“…It can easily be understood that removing of the bromine anion from 5a led to changing their characters from nucleophilic to electrophilic in accordance with previous studies. In this case, carbenoids as well as silylenoids can act as either nucleophiles or electrophiles …”

“…). It is clear that the ring opening to allene may also occur starting from free carbene . Then, free carbenes ( 8a , 8b , 8c , 8d , 8e , 8f , 8g , 8h , 8i , 8j ) have been considered as either singlet or triplet for the ring‐opening reaction mechanisms of the title structures.…”

“…In this case, carbenoids as well as silylenoids can act as either nucleophiles or electrophiles. [14][15][16]31,32] The molecular electrostatic potential (MEP) is most favored reactivity map to display the regions on organic molecules for the electrophilic and nucleophilic attacks. To determine reactive sites for electrophilic and nucleophilic attacks as well as hydrogen-bonding interactions for the title compound, the molecular electrostatic map (MEP) was performed at the B3LYP/6-31G(d) level of theory.…”

“…It is clear that the ring opening to allene may also occur starting from free carbene. [12,[14][15][16] Then, free carbenes (8a-j) have been considered as either singlet or triplet for the ring-opening reaction mechanisms of the title structures. Energy calculations depict that the structures of 8a-j are determined to be minima on the singlet state energy surface and energetically more stable than triplet ones at all the levels used herein.…”

“…This method, so-called DMS reaction, is well documented in the literature. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Interestingly, lowering the reaction temperature to À55°C leads to the formation of either cyclobutenes 3 (Route 2) or the compounds of 4 (Route 3) depending on the substituents of the spiropentane rings (Scheme 1). Although the synthetic and mechanistic aspects of the carbocationic skeletal rearrangements (Route 2 and 3) were investigated in detail many times by Zefirov et al, [10] no theoretical calculations about the conversions of lithium halogenospiropentanoids into the corresponding allenes and the substituent effects on this rearrangement have been reported so far (Route 1).…”