3- lithio-1-phenylsulfonyl

Direct 3-silylation of A -substituted indoles has been ellected by reaction of the indoles with trimethylsilyl triflate in the presence of triethylamine[12]. The trimethylsilyl group has also been introduced via 3-lithio-l-(phenylsulfonyl)-indole[13]. 

They transformed L-serine in seven steps to the iV-2-(trimethylsilyl)ethyl-sulfonyl(SES)-protected aziridine 104. The latter reacted with the lithio-an-ion of ( )-3-phenyl-l-(phenylsulfonyl)-2-propene (105) to a diastereomeric mixture of the sulfones 106 (Scheme 27). This mixture was treated with TBAF, yielding the pyrrolidine 107 as a single diastereoisomer with 2,3-frans-2,5-czs-configuration previously observed for 5-endo-trig cyclizations of this type. In three additional steps the pyrrolidine 107 was transformed to (+)-preussin (2), with 5% yield overall and in twelve steps altogether. 

A solution of 2-lithio-l-(phenylsulfonyl)indole was prepared by adding 1-(phenylsulfonyl)indole (11.7 mmol) dissolved in THF (30 ml) to a solution of LDA prepared from (i-Pr)2NH (1.12 eq) and n-BuLi (1.05 eq) in THF (30 ml) at — 75°C. The solution was stirred at — 70°C for 1 h and then warmed slowly to 5DC over 1 h. The solution was recooled to — 78JC. A solution of acetaldehyde (l.OOg, 22.7 mmol) in THF (5 ml) was added rapidly by syringe. The reaction mixture was then allowed to come slowly to room temperature and poured into 1% HC1 (350 ml). The solution was extracted with CH,C12 (3 x 250 ml) and the combined extract was washed with water (400 ml) and brine (2 x 400 ml) and then dried over K2C03. The solvent was evaporated in vacuo and the residue purified by chromatography to give the product (3.28 g, 93%). 

Optically active a -hydroxy acids The enolate of the amide (2) derived from phenylacetic acid and L-prolinol (10,332) is oxidized by 2-(phenylsulfonyl)-3-phen-yloxaziridine (1) to give optically active a-hydroxy amides (3). Significantly, the configuration of 3 depends upon the base. The lithio enolate (LDA) is converted to the (S)-isomer in >95% de, whereas the sodio enolate, generated with NaN[Si(CH3)3]2, is converted into the (R)-isomer in 93% de. 

Synthetic procedures are available for the preparation of fluoro (e.g., 2-lithio-l-methyl-5-octylpyrrole with fV-fluoro-iV-(phenylsulfonyl)benzenesulfonamide <2003JFC(124)159>), chloro, bromo, and iodo compounds from the corresponding lithio derivatives, for example, 2-iodobenzo[A]furan via lithiation of the heterocycle then reaction with iodine <2002JOC7048>. Perchloryl fluoride (FCIO3), A-chlorosuccinimide, bromine, and iodine are examples of reagents which can be used to introduce fluorine, chlorine, bromine, and iodine, respectively. 

Lithio-2-(phenylsulfonyl)oxiranes 362 (prepared by deprotonation of compounds 361) reacted with different electrophiles to give the expected products 363 which, by treatment with MgBr2 OEt2, afforded a-bromo carbonyl compounds 364 (Scheme 95)534-537. 

Methan (4-Chlor-phenylsulfonyl)-diethoxyphosphoryl-lithio- E19d,... 

C12HgBrLi02S Benzol 3-Brom-2-lithio-l-phenylsulfonyl- E19d, 402 (H -> Li)... 

Quinolizinium ions fused with indole are related to yohimbine alkaloids flavopereirine, sempervirine, reserpine, alstoniline, ajmaline, and so on. Parent indolo[2,3-a]quinolizinium salt (272) has been reported (87TL5259). l-Phenylsulfonyl-2-(2-pyridyl)indole 271 was treated with H-butyllithium to afford the 3-lithio species, which was quenched with bromoacetalde-hyde to give the cyclization product (48%). It was dehydrated with aq. NaOH to afford 272 (89%). Using this method, sempervirine (273) was obtained (88T3195). 

The electrophilic phosphonylation of chloromethyl phenyl sulfone in the presence of n-BuLi (2 eq) proceeds smoothly at low temperature, probably via the sulfone dianion, to give diethyl 1-lithio-1-chloro-l-(phenylsulfonyl)methylphosphonate. This is treated in situ with aliphatic or aromatic aldehydes and ketones to obtain a-chloro-a,(3-unsaturated ketones by the Homer-Wadsworth-Emmons reaction in good overall yields (76—85%)... 

Diethyl methylphosphonate reacts with phenylsulfonyl chloride (2 eq) in the presence of n-BuLi (3 eq) to produce diethyl 1-lithio-1,1-dichloromethylphosphonate, which can be quenched in quantitative yield or reacted directly with a large variety of carbonyl compounds (Homer-Wadsworth-Eimnons reaction), thus providing a useful one-pot process for the synthesis of dichloroalkenes. ... 

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