Reaction with mesylates

Preparation of the Living" Polystyrene. 18 g of the living polymer was prepared by standard anionic polymerization using n-butyl lithium. The reaction was carried out by the dropwise addition of 20 ml of styrene to 5 ml of the initiator solution in 150 ml of neat THF at -78°C. The styrene drip was adjusted to take approximately 30 min for completion and then the reaction was allowed to stir for two hours before the grafting reaction with mesylated lignin was carried out. The number average molecular weight of the polystyrene, as determined by HPSEC, was 9500 with polydispersity of 1.2. 

The diazoquinolinediones 22 were synthesized from the corresponding 4-hydroxy-2-quinolones through a diazotransfer reaction with mesyl azide. The rhodium(II) catalyzed Wolff rearrangement of the diones 22 in refluxing acetonitrile afforded oxindole derivatives 23 as a single product. 

The azidohydrins obtained by azide ion opening of epoxides, except for those possessing a tertiary hydroxy group, can be readily converted to azido mesylates on treatment with pyridine/methanesulfonyl chloride. Reduction and subsequent aziridine formation results upon reaction with hydrazine/ Raney nickel, lithium aluminum hydride, or sodium borohydride/cobalt(II)... 

A one-pot conversion of benzyl alcohols to benzyl fluorides by treatment of the alcohols with a combination of methanesulfonyl fluoride, cesium fluoride and 18-crown 6 ether in tetrahydrofuran has been repotted The reaction involves mesylation of the alcohols followed by cleavage of the resultant mesyl esters with a fluoride ion The reaction has been extended also to certain heterocycles bearing the N hydroxymethyl group [43] (equation 31)... 

The reaction of Ab-acetyl-1 -hydroxytryptamine (39) with mesyl chloride (MsCl) in THF in the presence of EtsN provides 1-acetyl-1,2,3,8-tetrahydropyrrolo[2,3-(j] indole (49a, 35%) (70JA343), Ab-acetyl-6-mesyloxytryptamine (50a, 4%), Ab-acetyl-2,3-dihydro-2-oxotryptamine (51a, 5%), l-acetyl-3a-(4-chlorobutoxy)-l,2,3,3a,8,8a-hexahydropyrrolo[2,3-(j]indole (52a, 7%), and Ab-acetyltryptamine (53a, 2%) as shown in Scheme 6 (2000H483). In the same reaction with MsCl, l-hydroxy-Ab-methoxycarbonyltryptamine (34) produces 50b (7%), 51b (34%), and 52b (9%), while the formation of 49b is not observed at all. In the case of Ab-trifluoroacetyl-l-hydroxytryptamine (48), 49c (45%), 50c (8%), 51c (4%), and 52c (6%) are produced. These data suggest that the yield of 49 increases, whereas the yield of 51 decreases in the order of electron-withdrawing ability of Ab substituents (COOMe < COMe < COCF3). Stability of 49 seems to govern the quantity of 51, which is probably formed by hydrolysis of 49. 

This tricyclic ring system was prepared from the functionalized pyrazo[l,5-n]pyridines. Thus, pyrazo[l,5-n]pyridine-3-carboxylate 462 gave 465 upon mesylation and subsequent reaction with 2-ethoxy-2-lithioxyethy-lene, whose cyclization afforded 466 (94AP435). Intramolecular aldol... 

Some alicyclic 1,2-diamine derivatives have recently been shown to have interesting CNS properties. For example, eclanamine (34) is an antidepressant with a rapid onset of action. The reasons for its potency are not as yet clear but pharmacologists note that the drug desensitizes adrenergic alpha-2 receptors and antagonizes the actions of clonidine. The synthesis of eclanamine starts with attack of cyclopentene oxide (30) by dimethylamine (to give 31). This product is converted to the mesylate by reaction with sodium hydride followed by mesyl chloride. Attack of... 

With a common intermediate from the Medicinal Chemistry synthesis now in hand in enantiomerically upgraded form, optimization of the conversion to the amine was addressed, with particular emphasis on safety evaluation of the azide displacement step (Scheme 9.7). Hence, alcohol 6 was reacted with methanesul-fonyl chloride in the presence of triethylamine to afford a 95% yield of the desired mesylate as an oil. Displacement of the mesylate using sodium azide in DMF afforded azide 7 in around 85% assay yield. However, a major by-product of the reaction was found to be alkene 17, formed from an elimination pathway with concomitant formation of the hazardous hydrazoic acid. To evaluate this potential safety hazard for process scale-up, online FTIR was used to monitor the presence of hydrazoic acid in the head-space, confirming that this was indeed formed during the reaction [7]. It was also observed that the amount of hydrazoic acid in the headspace could be completely suppressed by the addition of an organic base such as diisopropylethylamine to the reaction, with the use of inorganic bases such as... 

It is of interest that there exists a considerable amount of flexibility as to the substituent at C-21 in the acetonide series. For example, formation of the acetonide from 241 affords intermediate 242. Reaction with methanesulfonyl chloride gives the corresponding mesylate (243). Displacement... 

The stereoselective total synthesis of (+)-epiquinamide 301 has been achieved starting from the amino acid L-allysine ethylene acetal, which was converted into piperidine 298 by standard protocols. Allylation of 297 via an. V-acyliminium ion gave 298, which underwent RCM to provide 299 and the quinolizidine 300, with the wrong stereochemistry at the C-l stereocenter. This was corrected by mesylation of the alcohol, followed by Sn2 reaction with sodium azide to give 301, which, upon saponification of the methyl ester and decarboxylation through the Barton procedure followed by reduction and N-acylation, gave the desired natural product (Scheme 66) <20050L4005>. 

R2Cu(CN)Li2 reaction with vie-epoxy mesylatesA higher-order cuprate reacts selectively with the epoxide group of the epoxy mesylate 1 to provide 2 with inversion at C3. Ring closure of 2 furnishes the epoxide 3, which reacts with a second equivalent of the higher-order cuprate to furnish meso-4, with inversion at both C, and C3. This two-step reaction provides a route to acyclic alcohols with useful stereocontrol at both adjacent centers. 

Terminal propargylic mesylates are converted to alkylallenylzinc compounds by reaction with lithiotrialkylzincate reagents (Scheme 9.32) [117]. The latter are formed in situ from dialkylzinc and alkyllithium species. Deuterolysis of the allenylzinc intermediates gave rise to deuterated allenes (Eq. 9.138). 

Evidence for the mainly SN2 pathway for the silyl migration was obtained from reactions of enantioenriched mesylates (Eq. 9.153). The connfigurations of the alle-nylboronate intermediates were deduced from their reactions with cyclohexanecar-boxaldehyde to afford the anti products of known configuration (Eq. 9.154). It is assumed that these reactions proced by way of a cyclic transition state. 

The bromoallene (-)-kumausallene (62) was isolated in 1983 from the red alga Laurencia nipponica Yamada [64a], The synthesis of the racemic natural product by Overman and co-workers once again employed the SN2 -substitution of a propargyl mesylate with lithium dibromocuprate (Scheme 18.22) [79]. Thus, starting from the unsymmetrically substituted 2,6-dioxabicyclo[3.3.0]octane derivative 69, the first side chain was introduced by Swern oxidation and subsequent Sakurai reaction with the allylsilane 70. The resulting alcohol 71 was protected and the second side chain was attached via diastereoselective addition of a titanium acetylide. The synthesis was concluded by the introduction of two bromine atoms anti-selective S -substitution of the bulky propargyl mesylate 72 was followed by Appel bromination (tetrabromo-methane-triphenylphosphine) of the alcohol derived from deprotection of the bromoallene 73. 

Section 7.8). Other classes of derivatives are thus most conveniently prepared from the sulfonyl chloride. Reaction with an alcohol leads to formation of a sulfonate ester. Two common sulfonyl chloride reagents employed to make sulfonate esters from alcohols arep-toluenesulfonyl chloride, known as tosyl chloride, and methanesulfonyl chloride, known as mesyl chloride (see Section 6.1.4). Note the nomenclature tosyl and mesyl for these groups, which may be abbreviated to Ts and Ms respectively. 

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