**9. Catalytic α- and γ-alkylation of aldehydes and enals, a direct photoexcitation approach**

The α- and γ-alkylations of aldehydes and enals, respectively, are an important CdC bond forming reaction and very important in the building complex molecular architecture. These alkylations were reported as a photo-organocatalytic reaction where the product is enantioselective. The procedure is executed utilizing the commercially available aminocatalyst and carried out under the illumination of fluorescent light bulb in the absence of photoredox catalyst. The authors have demonstrated a strategy in which photochemical activation of substrates provides reactive radical species by the action of visible-light active photoredox catalyst. In this system the catalyst is chiral that acts as a dual catalytic system and provides an

easy access to chiral molecules as products in an asymmetric fashion. In a sense, in the reaction medium, the transiently generated enamines undergo electronic excitation by the action of light form reactive radical species from organic halides,

*Visible-Light Photocatalysis of Aldehyde and Carbonyl Functionalities, an Innovative Domain*

*DOI: http://dx.doi.org/10.5772/intechopen.92372*

**10. Photoredox cross-dehydrogenative coupling (CDC) of aldehydes with xanthenes (chiral enamines with diaryl compounds)**

Aldehydes under the treatment with visible light underwent catalytic asymmetric cross-dehydrogenative coupling reactions with xanthenes and thioxanthenes, and it is interesting to note that xanthenes are important candidates in the dye stuff

which, in turn, provide an effective stereochemical induction to yield

enantioselective alkylated products [14] (**Figures 14** and **15**).

**Figure 13.**

**141**

*Catalytic cycle of α-amination.*

**Figure 12.** *α-Amination of aldehydes.* *Visible-Light Photocatalysis of Aldehyde and Carbonyl Functionalities, an Innovative Domain DOI: http://dx.doi.org/10.5772/intechopen.92372*

**Figure 13.** *Catalytic cycle of α-amination.*

**8. Asymmetric α-amination of aldehydes by means of photoredox and**

*Photophysics, Photochemical and Substitution Reactions - Recent Advances*

The synthetic design and developing methodology on the creation of CdN bonds within the complex molecular architecture in a stereospecific manner is a challenging task which is routinely needed in the process development of drug molecules. Consequently, α-amino aldehydes are the valuable structural motifs in the process development of drug molecules. However, asymmetric α-amination of aldehydes poses a plethora of potential challenges since the reaction medium contains reagents and chemicals that can racemize product molecule. In this context, a VLPC methodology has been demonstrated for α-amination of aldehydes in an enantioselective fashion using nitrogen-centered radicals which enables the synthesis stable to racemization, a tactful synthetic methodology. N-centered radicals are easily generated using dinitrosulfonyloxy groups (ODNs) which are capable of producing the requisite heteroatom-centered radical upon exposure to household light and in the presence of designed catalyst. The nitrogen-centered radical thus is produced when treated with a transient π-rich enamine (derived from the coupling of an imidazolidinone catalyst with the aldehyde); upon photonic excitation, singleelectron transfer reaction produces nitrogen-centered radical. Then the reaction

proceeds to yield an iminium ion, which up on hydrolysis gives rise to enantiomerically enriched α-amino aldehyde [13] (**Figures 12** and **13**).

**9. Catalytic α- and γ-alkylation of aldehydes and enals, a direct**

The α- and γ-alkylations of aldehydes and enals, respectively, are an important CdC bond forming reaction and very important in the building complex molecular architecture. These alkylations were reported as a photo-organocatalytic reaction where the product is enantioselective. The procedure is executed utilizing the commercially available aminocatalyst and carried out under the illumination of fluorescent light bulb in the absence of photoredox catalyst. The authors have demonstrated a strategy in which photochemical activation of substrates provides reactive radical species by the action of visible-light active photoredox catalyst. In this system the catalyst is chiral that acts as a dual catalytic system and provides an

This is an organocatalytic and photoredox-based approach to the asymmetric α-amination of aldehyde, where a functionalized nitrogen is directly coupled with a formyl precursor. This protocol provides a ready access to N-substituted α-amino aldehyde architecture without any racemization with more than 85% enantiomeric

**organocatalysis**

excess.

**Figure 12.**

**140**

*α-Amination of aldehydes.*

**photoexcitation approach**

easy access to chiral molecules as products in an asymmetric fashion. In a sense, in the reaction medium, the transiently generated enamines undergo electronic excitation by the action of light form reactive radical species from organic halides, which, in turn, provide an effective stereochemical induction to yield enantioselective alkylated products [14] (**Figures 14** and **15**).
