Tosylate displacement

Another example of homoallylic tosylate displacement is the lithium... 

In continuation of the aforementioned reaction, Hiroya and coworkers used cop-per(II) acetate for the synthesis of indoles 2-943 in reasonable yields from the corresponding ethynylanilines 2-941 by a domino intermolecular Michael addition/cop-per-assisted nucleophilic tosylate displacement reaction via 2-942 (Scheme 2.211) [482],... 

The 1 R,6R,7R,8S-as-fused structure and conformation of 102 were elucidated on the basis of their NMR spectroscopic data. The observed formation of only one sulfonium salt in this cyclization reaction was remarkable in that either sulfur atom might have been expected to participate in tosylate displacement. The H NMR spectrum of salt 102 shows a large three-bond scalar coupling of 10.6 Hz between H-6 (5 = 4.736) and H-7 (5 = 4.606) this indicates that they have an almost antiperiplanar relationship. The equatorial orientation of H-6 and the 3C6 conformation of its six-membered cycle are consistent with the strong NOEs observed between H-7 and both H-2axja and and... 

Step 3 Tosylate displacement occurs with an inversion of stereochemistry. Step 4 The amine (free base) is isolated after a basic workup. 

Enolate formation at the less hindered a-position followed by intramolecular tosylate displacement affords Dl. 

FIG. 16. Synthesis of (+)-l,2,2-trimethyl-l,3-bis(diphenylphosphino)cyclopentane by tosylate displacement. 

Organometallic Reagents. The major product of the Dilithium Tetrachlorocuprate(II)- or Copper(I) /odide-catalyzed Grignard reaction in THF or ether at low temperature arises from epoxide opening rather than from direct tosylate displacement (Table... 

Further exploring the approach of nucleophiles to the carbonyl center, if the nucleophile is water, then orthoacids can be formed. However, orthoacids are very unstable and generally decompose to a mixture of two products. The first product is a derivative of the starting material with the tosylate displaced by hydroxide. In the second product, the acetate migrated from C-1 to C-2. With respect to mechanistic preferences, soft nucleophiles tend to favor ring opening, whereas hard nucleophiles tend to favor orthoester-type products. 

Nominally linear arrays of polyammonium ion systems have also been produced using a repetitive sequence of alkylation/tosylation/displace-ment based on a bicyclic diamino structure, l,4-diazabicyclo[2.2.2]oc-tane (Dabco ) (S9).46 Using this approach, strings , such as 40, can be prepared as shown in Scheme 5. 

An alternative approach would be to make the tosylate, displace with chlcride or bromide (Sf,j2 with inversion), then do a second inversion with NaSCH3... 

Figure 6.57 (b) A successful sulfonate displacement, (c) Dipole hindrance of tosylate displacements, (d) Sucralose. 

The thus established stereocenter served in the following steps. Conversion of 50 to 51 was achieved by acyl chloride formation followed by Friedel-Crafts reaction with ethylene and A1C13. Addition of the lithium enolate of t-butylacetate occurred from the less-hindered face of the cyclic ketone to give, after reduction and tosylation, adduct 52. Tosylate displacement with amine 53, esterification with methoxyacetylchloride, and addition of HC1 gave mibefradil 54. 

The gastric antisecretory properties of 15-deoxy-l 6-methyl-16-a,iS-hydroxyprostaglandin El methyl ester are associated exclusively with the 16(S) diastereomer 1054. Diol 1053, a key chiral synthon for the synthesis of 1054, is readily prepared from 1031 by conversion of the primary alcohol to a tosylate, displacement of the tosylate by mixed cuprate to give 1052, and then hydrolysis of the acetonide (Scheme 156) [222]. The overall yield of the sequence starting from (5)-citramalic acid is 50.4%. 

The lactone tosylate (43) reacts with dialkylcuprates or dialkenylcuprates selectively with tosylate displacement rather than ring opening to give (44). ... 

So, first the reduction of the ester to the corresponding primary alcohol with lithium aluminum hydride was effected, and the alcohol was converted to the toluenesulfonate (tosylate). Displacement by bromide anion (LiBr) to produce the primary bromide was followed by another lithium aluminum hydride reduction to the final hydrocarbon (Scheme 11.65). 

N-hexadecanoyl or N-eicosanoyl groups were synthesized from a 2-amino-2-deoxy-D-glucofuranoslde derivative via tosylate displacement by azide at Similar sulphonate dlsplacem.ent reactions... 

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