Epoxides, reaction with phenyl lithium

Reaction with epoxides. The reagent (1) in the presence of ZnU as catalyst converts epoxides into /3-siloxyalkyl phenyl selenides in 70-90% yield (cf. cleavage of epoxides with NaSeQHs, 5, 272-273). The facility of C—O bond cleavage is tertiary > primary > secondary. The selectivity follows the reverse order if n-butyl-lithium is used as the eatalyst. 

Reaction of the carbanion of chloromethyl phenyl sulphoxide 409 with carbonyl compounds yields the corresponding 0-hydroxy adducts 410 in 68-79% yield. Each of these compounds appears to be a single isomer (equation 242). Treatment of adducts 410 with dilute potassium hydroxide in methanol at room temperature gives the epoxy sulphoxides 411 (equation 243). The ease of this intramolecular displacement of chloride ion contrasts with a great difficulty in displacing chloride ion from chloromethyl phenyl sulphoxide by external nucleophiles . When chloromethyl methyl sulphoxide 412 is reacted with unsymmetrical ketones in the presence of potassium tcrt-butoxide in tert-butanol oxiranes are directly formed as a mixture of diastereoisomers (equation 244). a-Sulphinyl epoxides 413 rearrange to a-sulphinyl aldehydes 414 or ketones, which can be transformed by elimination of sulphenic acid into a, 8-unsaturated aldehydes or ketones (equation 245). The lithium salts (410a) of a-chloro-/ -hydroxyalkyl... 

A chiral, nonracemic oxirane, (3 )-2-[(R)-fluoro(phenyl)methyl]oxirane, can react with (chiral) amines under the influence of lithium perchlorate using either heat or microwave irradiation. This reaction sequence provides a material from which the ee of chiral a-branched amines can be determined <2005OL3829>. Guanidines serve as a useful nitrogen nucleophile for the direct conversion of epoxides to aziridines <2004JOC8504>. 

Chiral amino alcohols can be prepared by reaction of chiral epoxides with amines. Enantiopure (25, 3.R)-2,3-epoxy-3-phenylpropanol anchored to Merrifield resin has been used for ring-opening with secondary amines in the presence of lithium perchlorate to afford polymer-supported chiral amino alcohols 47 (Eq. 18) [56], By analogy, (2i ,35)-3-(cis-2,6-dimethylpiperidino)-3-phenyl-l,2-propanediol has been anchored to a 2-chlorotrityl chloride resin (48). Although this polymer had high catalytic activity in the enantioselective addition of diethylzinc to aldehydes, the selectivity of the corresponding monomeric catalyst was higher (97 % ee) in the same reaction. 

Nine- and Ten-membered Rings.—Ring-forming Reactions. Treatment of transjrans-farnesyl phenyl sulphide with N-bromosuccinimide and sodium carbonate gave mon-epoxide (58), which cyclized on treatment with n-butyl-lithium and DABCO to give a mixture of (59 R = SPh) and its 2,3-cis-double bond isomer (total yield of 60%). Removal of the phenylthio-group by lithium-ethylamine reduction gave a mixture of (59 R = H) and (60). ... 

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