Ab initio computational study of 1-methyl-4-silatranone and attempts at its conventional synthesis

作者：Morgan Jessica P; Weaver Guevara Holly M; Fitzgerald Ryan W; Dunlap Smith Azaline; Greenberg Arthur^*

来源：Structural Chemistry, 2017, 28(2): 327-331.

DOI：10.1007/s11224-016-0871-1

• Silatrane
• Lactam
• Amide
• Resonance energy

1-Methyl-4-silatranone could exhibit the structural aspects of a typical silatrane including a short N-Si bond distance reflecting a dative bond. But given the significant amide resonance in a [3.3.3] bridgehead bicyclic lactam, the lone pair could be shared with the carbonyl group leading to a very long N-Si bond, essentially a "non-silatrane." Ab initio calculations (MP2/6-311 + G*) predict that ground state conformations of this molecule are best regarded as lactams rather than silatranes, the most stable having a calculated N-Si bond length of 2.902 and an N-CO bond length of 1.387 . The calculated transition state for inversion of the amide ring retains very little amide resonance (N-CO, 1.440 ). Some of this loss is compensated through tightening of the N-Si bond (2.422 ), leading to a net energy of activation of ca 8 kcal/mol. Attempts to synthesize 1-methyl-4-silatranone using conventional pathways successful for 1-methylsilatrane [condensations employing N,N-bis(2-hydroxyethyl)glycolamide in place of tris(2-hydroxyethyl)amine] were unsuccessful. This is due to the net loss in resonance energy of the amide reactant relative to that in the [3.3.3] system, the essential absence of the N-Si dative bond, and the rigidity introduced by the planar amide linkage in the starting material. A more likely pathway to successful synthesis should be formation of the amide linkage in the final step.

• 出版日期2017-4