The first general organocatalytic Beckmann rearrangement of ketoximes into amides has been realized by the catalytic use of cyanuric chloride. Furthermore, acids such as HCl and ZnCl2 are effective as cocatalysts with cyanuric chloride. For example, azacyclotridecan-2-one, which is synthetically useful as a starting material for nylon-12, was prepared in quantitative yield by the Beckmann rearrangement of cyclododecanone oxime (100 mmol scale) catalyzed by cyanuric chloride (0.5 mol %) and ZnCl2 (1 mol %).
Proper design of acid-base catalysis has been shown to be effective for achieving high reactivity and selectivity in the asymmetric direct aldol reaction during the development of diamine-Brønsted acid types of catalyst. In this study, two principal approaches have been implemented to create a new type of catalysis and high catalytic efficiency: one is the creation of a highly viable acidic function within acid-base catalysts; the other is the creation of rather complicated but more cooperatively arranged hydrogen-bond networks that would be expected to stabilize a transition state, thereby promoting new reactivity and selectivity.
The use of the tris(trimethylsilyl)silyl (TTMSS) group in aldehyde-derived silyl enol ethers affords aldehyde cross-aldol products with high yields and allows for unprecedented reactivity. The reaction is catalyzed by 0.05 mol % of HNTf2, and can easily be managed to give beta,delta-bis-, beta,delta,gamma-tris-, and beta,delta,zeta-tris-hydroxy-aldehydes with extremely high selectivity by simple stoichiometric control. High diastereoselectivity is obtained in all cases, and the use of chiral aldehydes affords Felkin products when there are nonchelating substituents, chelation products when there is a chelating sbustituent, and syn products when there is beta-substitution. HNTf2 is proposed to be an initiator, and highly Lewis acidic TTMSSNTf2 is the true catalyst.
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