167389-29-9Relevant academic research and scientific papers
Asymmetric synthesis of substituted homoallyl alcohols, halomethyl tetrahydrofurans, and chloro-amino sulfones from allyltitanium sulfoximines and α-hetero aldehydes
Rajender,Gais, Hans-Joachim
, p. 579 - 582 (2008/02/02)
Asymmetric syntheses of the iodomethyl-substituted bicyclic tetrahydrofuran 22 and the chloro-amino sulfone 30 from the allylic sulfoximine 15 and the α-hetero aldehydes 2 and 23, respectively, are described. Further examples for the asymmetric synthesis
Asymmetric Synthesis of 2,3-Dihydrofurans and of Unsaturated Bicyclic Tetrahydrofurans through α-Elimination and Migratory Cyclization of Silyloxy Alkenyl Aminosulfoxonium Salts. Generation and Intramolecular O, Si-Bond Insertion of Chiral Disubstituted β-Silyloxy AlkyHdene Carbenes
Gais, Hans-Joachim,Reddy, Leleti R.,Babu, Gadamsetti S.,Raabe, Gerhard
, p. 4859 - 4864 (2007/10/03)
Treatment of the bis(allylsulfoximine)titanium complexes derived from the β-methyl-substituted acyclic allylic sulfoximines 13a and 13b with aldehydes gave with high selectivities the corresponding sulfoximine-substituted homoallylic alcohols which were isolated as the silyl ethers 15a-h. Methylation of sulfoximines 15a-h afforded the aminosulfoxonium salts 5a-h which upon treatment with LiN(H)tBu gave in high yields the enantio- and diastereomerically pure silyl-substituted 2,3-dihydrofurans 4a-h. Treatment of the titanium complexes derived from the cyclic allylic sulfoximines 17a, 17b, and ent-17c with p-MeOC6H4-CHO delivered with high selectivities the corresponding sulfoximine-substituted cyclic homoallylic alcohols which were isolated as the silyl ethers 18a, 18b, and ent-18c, respectively. Methylation of sulfoximines 18a, 18b, and ent-18c furnished the aminosulfoxonium salts 8a, 8b, and ent-8c, respectively, whose treatment with LiN(H)t-Bu gave the enantio- and diastereomerically pure fused bicyclic 2,3-dihydrofurans 6a, 6b, and ent-6c, respectively, in good yields. It is proposed that the 1-alkenyl aminosulfoxonium salts 5a-h, 8a, 8b, and ent-8c react with the base under α-elimination and formation of the acyclic and cyclic β-silyloxy alkylidene carbenes 2a-h, 7a, 7b, and ent-7c, respectively, which then undergo a 1,5-O,Si-bond insertion and 1,2-silyl migration. The cyclic aminosulfoxonium salts 8a, 8b, and ent-8c upon treatment with 1,8-diazabicyclo[5.4.0]-7-undecene did not undergo an α-elimination but suffered a novel migratory cyclization with formation of the enantio- and diastereomerically pure bicyclic tetrahydrofurans 9a, 9b, and ent-9c, respectively. It is proposed that the 1-alkenyl sulfoxonium salts 8a, 8b, and ent-8c are isomerized to the allylic aminosulfoxonium salts 10a, 10b, and ent-10c, respectively, which then suffer an intramolecular substitution of the (dimethylamino)sulfoxonium group by the silyloxy group followed by a desilylation. The syntheses of the 2,3-dihydrofurans 4a-h, 6a, and 6b and of the tetrahydrofurans 9a and 9b are accompanied by the formation of sulfinamide 16 of ≥98% ee, which can be converted via sulfoxide 28 of ≥98% to the starting sulfoximine 11 of ≥98% ee.
Regio- and enantioselective substitution of primary endocyclic allylic sulfoximines with organocopper and organocuprate reagents. The importance of iodide for the allylic substitution with organocopper compounds
Gais, Hans-Joachim,Müller, Harald,Bund, J?rg,Scommoda, Matthias,Brandt, Jochen,Raabe, Gerhard
, p. 2453 - 2466 (2007/10/02)
The endocyclic N-substituted allylic sulfoximines 17-20 and 26 were synthesized from the corresponding cycloalkanones and the various (S)-5-(lithiomethyl)-S-phenylsulfoximines in enantiomerically pure form in yields of 60-70% in a process involving the isomerization of the intermediate vinylic sulfoximines. Desilylation of 26 gave the parent N-H sulfoximine 27 from which the N-sulfonylsulfoximines 28 and 29 were prepared. The X-ray crystal structure of 28 was determined. The allylic sulfoximines 17-20 and 26-29 did not racemize or rearrange thermally to the corresponding allylic sulfinamides. Reaction of the allylic sulfoximines 18, 28, and 29 with the organocuprate reagents 2/LiI, 35/LiI, and 47/LiI led with α-selectivities of 92:8 to 99:1 to the endocyclic alkenes 39 in good to high yields. Reaction of 17-20, 28, and 29 with the organocopper reagents 5/LiI, 30/LiI, 31/LiI, 32/LiI, 33/LiI, 34/LiI, and 37/LiI in the presence of BF3 resulted in the formation of the exocyclic alkenes 38, 41, 43, and 45, respectively, in good to high yields with γ-selectivities of 80:20 to 99:1. The sulfonimidoyl group imparts asymmetric induction to the substitution in the range of 27-90% ee. The (S)-sulfonimidoyl group leads to a preferential bond formation from the si side of the double bond. From the sulfoximines 18 and 26-29 the N-methylsulfoximine 18 and the N-tosylsulfoximine 28 showed the highest and lowest reactivity with the butylcopper reagent 32/LiI in the presence of BF3, respectively, while in the absence of BF3 only 29 reacted. The Lewis acid most likely serves to activate the N-methyl- and N-tosylsulfoximines or intermediates thereof through coordination at the sulfonimidoyl and sulfonyl group. Reaction of the sulfoximines 18 and 29 with pure Me3SiCH2Cu (34) revealed a strong rate acceleration by LiI and an even stronger one by Bu4NI. This points to the existence of a heteroleptic cuprate or a related compound as reactive species. In substitutions with the Yamamoto reagents RCu/MX/BF3, the halide is important and a reaction between RCu and BF3 does not have, at least in the case of allylic sulfoximines, to be invoked. In reactions of 17-20 besides the alkenes, the sulfinamide ent-4 was formed with an ee value of 97% in high yield with retention of configuration. The absolute configuration of the exocyclic alkenes 38, 41, and 45 was determined by ozonolysis to the corresponding cycloalkanones followed by their conversion to the corresponding lactones and/or CD measurement of the former.
