In this case, there is an electronegative atom containing a lone pair of electrons. Here, also classification of the groups into large, medium and small group. As a result of the overlap between C-N σ* antibonding orbital π*of the carbonyl makes this conformation shown below even more important.  This result is in great increase in the degree of diastereoselectivity (Scheme 12).

Scheme 12

In case of cyclohexanone derivatives the addition of a nucleophile generates either a conformation with the nucleophile at an equatorial or an axial position. However, unless the molecule is locked in a particular conformation, it does not matter whether the nucleophile is attacking a line to the equatorial or axial position since a ring inversion can put the molecule in a favourable conformation. However, in 4-^tbutylcyclohexanone, the t-butyl group always occupies equatorial conformation. Now, with the increase in steric bulk of the attacking nucleophile, there will be tendency to attack at the equatorial position as compared to the axial position. Thus, the reduction of 4-^tbutylcyclohexanone with LiAlH₄ gives mostly trans alcohol while Grignard addition of C₂H₅MgBr affords cis-alcohol (Scheme 13).

Scheme 13