Functionalized Chiral Vinyl Aminosulfoxonium Salts: Asymmetric Synthesis and Application to the Synthesis of Enantiopure Unsaturated Prolines, β,γ-Dehydro Amino Acids, and Cyclopentanoid Keto Aminosulfoxonium Ylides
摘要:
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.
hydroxyalkylation of allylic N-methyl sulfoximines 1–4 gave with ≥ 95% de the anti-Z-configurated homoallylic alcohols 5–9. Lithiation of 6b and 8b with MeLi readily produced the lithiated vinylic sulfoximines (Z)-12 and (Z)-13, respectively. Ni-catalyzed substitution of (Z)-12 and (Z)-13 with PhLi and 1,5-silyl migration yielded with ≥ 98% de the disubstituted C-silylated homoallylic alcohols (Z)-14 and (Z)-15
Stereoselective hydroxyalkylation of titanated allyl sulfoximines at the α-as well as the γ-position through variation of the titanation reagent
作者:Rüdiger Hainz、Hans-Joachim Gais、Gerhard Raabe
DOI:10.1016/0957-4166(96)00318-7
日期:1996.9
Titanation of the lithioallyl sulfoximines E-2 and 2-2 with ClTi(NEt(2))(3) gives allyltitanium species which react with aldehydes highly regio- and diastereoselectively at the alpha-position to form the syn-alpha-hydroxalkyl allyl sulfoximines E-3 and Z-3, respectively. With ClTi(OiPr)(3) as the titanation reagent anti-gamma-hydroxyalkyl vinyl sulfoximines are obtained instead with equally high selectivities. NMR spectroscopic evidence points to the formation of the monoallyltitanium sulfoximine E-l upon reaction of E-2 withClTi(NEt(2))(3). Copyright (C) 1996 Elsevier Science Ltd