title: Functionalized chiral vinyl aminosulfoxonium salts: asymmetric synthesis and application to the synthesis of enantiopure unsaturated prolines, beta,gamma-dehydro amino acids, and cyclopentanoid keto aminosulfoxonium ylides.
abstract: Methylation of the enantiopure functionalized vinyl sulfoximines 5a-e and 14a-d followed by a F- ion or DBU-mediated isomerization of the vinyl aminosulfoxonium salts 7a-e and 15a-d, respectively, gave the allyl aminosulfoxonium salts 10a-e and 17a-d, respectively. A concomitant intramolecular substitution of the aminosulfoxonium group of 10a-e and 17a-d by the amino group afforded the unsaturated prolines 8a-e and 18a-d, respectively. The starting vinyl sulfoximines are accessible through a highly selective and stereo-complementary aminoalkylation of the corresponding sulfonimidoyl-substituted mono- and bis(allyl)titanium complexes with the imino ester 4. The vinyl aminosulfoxonium salts 34, 7a-d, and E-15c experienced upon treatment with the Cl- ion a migratory substitution with formation of the delta-chloro-beta,gamma-dehydro amino acids 36, E/Z-37a-d, and 38, respectively. A migratory substitution of the hydroxy-substituted vinyl aminosulfoxonium salts 46a and 46b furnished the delta-chloro allyl alcohols E/Z-48a and E-48b, respectively. A facile one-pot conversion of the vinyl sulfoximines 31b, 5c and 45a to the allyl chlorides 36, E/Z-37c and E/Z-48a, respectively, was achieved upon treatment with a chloroformiate. A tandem cyclization of the vinyl aminosulfoxonium salts 7b, Al-7b and 57 with LiN(H)tBu yielded the cyclopentanoid keto aminosulfoxonium ylides 54, Al-54, 59, 60 and 61, respectively. The structure of the tricyclic keto aminosulfoxonium ylide Al-54 has been determined by X-ray crystal structure analysis. Ab initio calculations and a NBO analysis of the tricyclic keto aminosulfoxonium ylide XXIII show a polar structure stabilized by electrostatic interactions between the ylidic C atom and both the carbonyl C atom and the S atom.
authors.affiliation: Institut für Organische Chemie der Rheinisch-Westfälischen Technischen Hochschule (RWTH) Aachen, Landoltweg 1, D-52056 Aachen, Germany.
authors.forename: Shashi Kant
authors.initials: SK
authors.lastname: Tiwari
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Gais
authors.forename: Andreas
authors.initials: A
authors.lastname: Lindenmaier
authors.forename: Gadamsetti Surendra
authors.initials: GS
authors.lastname: Babu
authors.forename: Gerhard
authors.initials: G
authors.lastname: Raabe
authors.forename: Leleti Rajender
authors.initials: LR
authors.lastname: Reddy
authors.forename: Franz
authors.initials: F
authors.lastname: Köhler
authors.forename: Markus
authors.initials: M
authors.lastname: Günter
authors.forename: Stefan
authors.initials: S
authors.lastname: Koep
authors.forename: Vijaya Bhaskara Reddy
authors.initials: VB
authors.lastname: Iska