Copper-Catalyzed Synthesis of Esters from Ketones. Alkyl Group as a Leaving Group. akatani, Y.; Koizumi, Y.; Yamasaki, R.; Saito, S. rg. Lett. 2008, 10, 2067-2070. An Annulation Reaction for the Synthesis of Morpholines, Thiomorpholines, and Piperazines from B-eteroatom Amino Compounds and Vinyl Sulfonium Salts Yar, M.; McGarrigle, E.; Aggarwal, V. Angew. Chem. Int. Ed. 2008, 120, 3844-3846. ibbs Short Literature Presentation August 12, 2008
Alkyl Group as a Leaving Group catalytic cleavage of C-C bonds by transition metal complexes a b R 1 R 2 2 path a Pd II or Ru R 1 R 2 path b R 1 C 3 Shimada, T.; Yamamoto, Y. J. Am. Chem. Soc. 2003, 125, 6646-6647. catalytic cleavage typically of activated substrates R 2 Et [ReBr(C) 3 (thf)] 2, C 2 C Et Kuninobu, Y.; Kawata, A. J. Am. Chem. Soc. 2006, 128, 11368-11369. akatani, Y.; Koizumi, Y.; Yamasaki, R. Saito, S. rg. Lett. 2008, 10, 2067-2070.
R Surprise, Surprise Cu bronze (5 mol %) (10 mol %) R I n-bu 2 (1.2 equiv), DMF, 100 C 2 Cu bronze (5 mol %) I (10 mol %) n-bu 2 (1.2 equiv), DMF, 100 C 2 conversion of ketones to esters by alkoxylation-dealkylation n-bu I Koizumi, Y.; Saito, S. Tetrahedon Letters, 2005, 46, 4715-4717.
Copper-Catalyzed Synthesis of Esters from Ketones R n-bu 4 2 (1.2 equiv) CuI (10 mol %), ligand o-xylene, 150 C, 6h n-bu R ligand (mol %) yield (%) none (no catalyst) 0 none 21 1,10-phenanthroline (L1) (20) 26 L1 (10) 3 Et L1 (10) 14* n-bu i-pr L1 (10) 76 Cu-catalyzed reaction 2 alkyl > 1 alkyl >> aryl, 3 alkyl R = Cy, t-bu, yield = 0% migratory aptitude of alkyl groups Baeyer-Villigar reaction 3 alkyl > 2 alkyl, aryl > 1 alkyl akatani, Y.; Koizumi, Y.; Yamasaki, R. Saito, S. rg. Lett. 2008, 10, 2067-2070.
Generality of the Reaction i-pr n-bu 4 2 (1.8 equiv) CuI (10 mol %) L1 (10 mol %) o-xylene, 150 C n-bu aryl ispropyl ketones with a EDG such as,, t-bu converted aryl ispropyl ketones with a EWG (Cl, CF3, 2) also converted 2 Ci-Pr aminoketone eliminated by Sandmeyer-type reaction 2 R S CuCl 2 TF, 40 C R S 3 volatile leaving group (ipr) eliminated preferentially akatani, Y.; Koizumi, Y.; Yamasaki, R. Saito, S. rg. Lett. 2008, 10, 2067-2070.
chanistic ypothesis i-pr n-bu 4 2 (1.8 equiv) CuI (10 mol %) L1 (10 mol %) o-xylene, 150 C n-bu n-bu 4 2 n-bu Cu III Cu I n-bu Cu III bulky i-pr group facilitate conversion of tetrahedral intermediate to the ester Cu III 2 n-bu akatani, Y.; Koizumi, Y.; Yamasaki, R. Saito, S. rg. Lett. 2008, 10, 2067-2070.
Conclusion i-pr n-bu 4 2 (1.8 equiv) CuI (10 mol %) L1 (10 mol %) o-xylene, 150 C n-bu synthesis of esters using tetraalkylammonium nitrites and copper catalyst less activated C C bond is cleaved alkyl group is the leaving group!!! akatani, Y.; Koizumi, Y.; Yamasaki, R. Saito, S. rg. Lett. 2008, 10, 2067-2070.
Morpholines, Thiomorpholines, and Piperazines S morpholine thiomorpholine piperazine C 3 C 3 S 3 chenolin A antimicrobial and anti-inflammatory activity imatinib (Gleevec) leukemia drug
Synthetic Routes for Annulation Direct Synthesis R 2 = Cl, Br low yields, side reactions, competing elimination R R =, S, [] one-step process? Three-step Process R R R 2
Soft Electrophiles for Ring Closure need to minimize/eliminate competing elimination pathways S 2 Tf vinyl onium salts as Michael acceptors
Soft Electrophiles for Ring Closure need to minimize/eliminate competing elimination pathways S 2 Tf vinyl onium salts as Michael acceptors Tf R 1 S 2 R 1 S 2 R 1 S 2 R 1 S 2 R 2 R 2 R 2 R 2 =, S, one-step process? YES!
Soft Electrophiles for Ring Closure S 2 Tf vinyl onium salts as Michael acceptors Br Tf 2 S, reflux, 5 h 81% Br Tf S 2 KC 3 TF/ 2, rt, 20 min 96% S 2 Tf leaving group ability important ( S > >> P)
R 1 Substrate Scope S Tf 2 R 2 Et 3 (2-3 equiv), C 2 Cl 2, 0 C rt, 15 h R 1 R 2 substrate product yield (%) 2 C 2 C 97 Ts Ts no racemization! 2 C s S 2 Cl 2 2 2 C s S Cl 98 94 91
Practical Application of thodology 2 C 2 Cl 1. TsCl, Et 3 2. Et 3, C 2 Cl 2, 0 C rt, 15 h 2 C Ts, 45% Br in C 3 C 2, rt, 16 h 94% 2 C S 2 Tf 97% 5M Cl Fmoc-Cl, ac 3 2 C Fmoc dioxane, reflux, 16 h 98% 2 C Fmoc 99% 84% overall yield no racemization
Conclusion R 1 S Tf 2 R 2 Et 3 (2-3 equiv), C 2 Cl 2 =, S, R 1 R 2 91-99% yield one step synthesis of morpholines, thiomorpholines, and piperazines from B-amino alchohols/thiols/amines no redox processes diphenyl vinyl sulfonium trifilate acts as bis-electrophile that eliminates elimination pathways)