Diazepane Carboxylates as Organocatalysts in the Diels–Alder Reaction of α‐Substituted Enals. Issue 39 (12th October 2018)

• Record Type: Journal Article
• Authors: Häggman, Nicklas O.; Zank, Benjamin; Jun, HyunJune; Kaldre, Dainis; Gleason, James L.
• Is Part Of: European journal of organic chemistry. Issue 39(2018)
• Page Start: 5412
• Page End: 5416
• Publication Date: 2018-10-12
• Subjects: Organocatalysis -- Diels–Alder -- Hydrazide -- Electrostatic interactions -- A‐1, 3 strain; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201801009
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract : Ethyl diazepane carboxylate efficiently catalyzes the Diels–Alder cycloaddition of α‐substituted‐α, β‐unsaturated aldehydes via iminium ion organocatalysis. The reaction is applicable to a range of dienes and dienophiles and generally proceeds at room temperature in the presence of 5 mol‐% catalyst and 2.5 mol‐% triflic acid co‐catalyst. The incorporation of a stereogenic center on the diazepane backbone in combination with a menthyl carbamate produces a catalyst which affords enantioselectivities of 70–95 % ee for the cycloaddition of cyclopentadiene with a range of dienophiles. The enantioselectivity is rationalized via a transition state in which electrostatic stabilization by the carboxylate directs the diene to the more hindered face of the dienophile. Abstract : Diazepane carboxylates efficiently catalyze the Diels–Alder cycloaddition of α‐substituted enals with a range of dienes. With chiral diazepane backbones, weak electrostatic interactions favour diene approach from the more hindered face, leading to enantioselectivities of 70–95 % with a range of dienophiles.