Pei-Pei Paper Questions

Front

What is the favored transition state (TS4-(Re)) in DFT analysis?

Back

The favored TS4-(Re) is 1.6 kcal/mol more stable than the disfavored TS4-(Si) due to increased steric repulsion in TS4-(Si).

Front

What is the primary source of enantioselectivity in the DFT analysis?

Back

Increased steric repulsion between the σ-allyl CH2 group and the ligand in TS4-(Si), causing higher distortion energy (ΔΔE_dist).

Front

What is the significance of the C-H...Cl hydrogen bond in TS4-(Re)?

Back

The C-H...Cl hydrogen bond is significantly shorter and stronger in TS4-(Re) (2.41 Å) compared to TS4-(Si) (2.42 Å), contributing to its stability.

Front

What is the general rule for C-C coupling at the azine C=N site?

Back

C-C coupling occurs at the azine C=N site with the largest LUMO coefficient.

Front

For which substrates does the C-C coupling rule fail?

Back

The rule fails for 2f and 2g (nitropyridines) because their LUMO is localized on the nitro group.

Front

What is the computational explanation for the failure of the C-C coupling rule for nitropyridines?

Back

Regioselectivity is controlled by the LUMO+1 orbital instead of the LUMO.

Front

What is the hapticity of the allyl group in the key intermediate (Int6)?

Back

Int6 is a π-allyl (η3) complex.

Front

How does the hapticity change in the transition state (TS4)?

Back

Int6 must isomerize to a σ-allyl (η1) haptomer to act as the nucleophile in TS4.

Front

What are the mechanistic steps in the alkyne-to-allene isomerization?

Back

1) Migratory insertion, 2) β-H elimination, 3) Allene migratory insertion.

Front

What is the role of β-H elimination in the isomerization process?

Back

β-H elimination is a key step that facilitates the transformation from alkyne to allene.