Facial Diastereoselectivity in the Paternò–Büchi Reaction of Chiral Silyl Enol Ethers

Abstract

A single element of chirality determines the configuration of the three newly formed stereogenic centers in the title reaction [Eq. (a)]. In particular, large (R = SiMe2Ph,tBu) and polar (R = OMe) substituents induce good diastereoselectivities. Simple ring‐opening reactions facilitate a stereoselective approach to acyclic products.

Stereoselective Intermolecular [2 + 2]-Photocycloaddition Reactions and Their Application in Synthesis

“…Good acyclic facial diastereoselectivities were achieved in the photocycloaddition of chiral silyl enol ethers V to aromatic aldehydes. 205 Due to 1,3-allylic strain the defined conformation V¢ shown in Figure 3 is preferred for b-substituted silyl enol ethers with a stereogenic center in the g-position.…”

Oxetane Synthesis through the Paternò-Büchi Reaction

“…The presence of a stereogenic center in the β-alkyl group (as in 18 ) induced a facial diastereoselectivity. In some cases, high diastereoisomeric ratios were observed (Scheme 13) [85].…”

“…In this case, a fluoride-promoted cleavage can be used to open the oxetane ring [85]. When the chiral center is in α position low facial diastereoselectivity was observed [86].…”

A DFT Study of 1,4‐Biradical Intermediates Involved in Stereoselective Paternò–Büchi Reactions

“…The presence of a stereogenic carbon atom in the β‐alkyl group (as in 4 ) induced a facial diastereoselectivity with high diastereoisomeric ratios in some cases (Scheme ) 9. The diastereoselectivity is probably due to the presence of a conformational preference represented in Figure 1, which allows the Si attack 10…”