we have investigated the possibility of proton transfer from the naphthol additive to the quinuclidine nitrogenfor theBzCPD catalyst case. The deprotonation of naphthol with the concomitant protonation of the quinuclidine nitrogen was seen to be not possible, as the quinuclidine nitrogen gave back the proton to the oxygen of the naphthol (see Fig. in SI).It is likely that other additives such as R-BINOL, which have a similar structure, will also not be able to directly react with the catalyst or substrate. Therefore, such minor side reactions have been ignored in the current work. Moreover, the dual complexation indicated here (hydrogen bonding and π stacking) would be significantly preferred to the additive solely interacting with one of the substrates through hydrogen bonding (as has been suggested in all the experimental reports considered in the current study). It is, however, noteworthy, that for two cases (entries 6 and 9 in Table ), the complexation was seen to be unfavourable, i.e., such a sandwiched complex would not be formed. This result indicates that while such a possibility is present in the majority of the additives that have been experimentally employed, there do exist cases where the aromatic additive would not function in this fashion. In these cases, any observed improvement in yield or enantioselectivitywould be due to the other reasons mentioned in the literature: improvement in the pKa of the reaction, or because of the aromatic additive hydrogen bonding with one of the substrates. In order to investigate the mechanism of Chen's thiocyanation reaction with 2-naphthol as additive, we considered the system comprising of the catalyst, BzCPD, the electrophile, N- compared to the Wynberg ion-pair hydrogen bonding pathway. Therefore, such a transfer thiocyanation pathway has not been studied in the current work. It is also to be noted that, due to the available conformational space between the C6'-OH and the quinuclidine NH of the catalyst, the nucleophile can approach in both the syn or anti fashions to give different syn-S, syn-R and anti-S, anti-R products (see Fig. in SI). We considered all the approaches to find the best approach. It was seen the syn approach was favoured over the anti by 6.3 kcal/mol(see Fig. in SI). Therefore the complete pathway for the thiocyanation was then studied for the syn approach pathway.The energy profile for the Wynberg ion-pair hydrogen bonding model, which is the most favorable pathway for the thiocyanation reaction with the 2-naphthol additive, is presented in Fig. . In the dual activation mechanism shown in Fig. above, the formation of the hydrogen-bonded complex Intrm1 between the oxindole and catalyst OH is energetically favoured by 5.7 kcal/mol. The proton transfer from the oxindole carbon to the quinuclidine nitrogen takes place after surmounting a barrier of 5.1 kcal/mol. This leads to the ion-pair complex Intrm2, which is 7.1 kcal/mol more stable than the totally separated reactant species.