Tosylamidate ions

Anions of secondary-sulfonamides, especially N-substituted tosylamidate ions, have emerged as premier partners for C-N bond forming reactions with alkynyliodonium salts. To a much lesser extent secondary-carboxamidate ions have also been used for this purpose. For example, the sequential treatment of -substituted tosylamides with n-butyllithium and phenyl(trimethylsi-lylethynyl)iodonium triflate (26) affords the corresponding N-trimethylsi-lylethynyl-p-toluenesulfonamides, which can be desilylated with tetrabutylam-monium fluoride in wet THF (Scheme 51) [ 151 ]. It is noteworthy that the presence of such groups as n-Bu and CH2 = CH(CH2)2- in the tosylamidate ions did... 

Reactions of phenyl(propynyl)iodonium triflate (30) with tosylamidate ions possessing N-alkyl chains of two or more carbon atoms follow the carbene insertion pathway leading to AT-tosyldihydropyrroles 31 (Scheme 54) [154,155]. The N-cyclohexyl tosylamidate ion leads stereospecifically to the ds-fused bicyclic dihydropyrrole under these conditions. 

Similar reactions of allylic tosylamidate ions with 30 provide access to azabi-cyclo[3.1.0]hexanes 40, possessing an exocyclic double bond [167]. Such compounds (generated in situ) have been utilized for the synthesis of ds-l-acetyl-2-tosylamidocyclopropanes (Scheme 61) [168]. 

Changing the metal carbonate also affected intramolecular cyclization to form the 10-membered macrocycle with three nitrogen atoms in the ring. Isolated yields were 0%, 21%, 75%, 75%, and 0% using lithium, sodium, potassium, cesium, and silver ions, respectively (Chavez and Sherry, 1989). This indicates that potassium and cesium carbonates are excellent bases for the deprotonation of the tosylamides in DMF and that a template effect is not the most important factor in this reaction. 

Aftalion and Proctor71 examined the mass spectra of several tosylamides, derived from cyclic and aromatic amines, in the attempt to draw some generalizations on the electronic or conformational requirements which rendered the molecular ion prone to loss of S02. 

Related with the previous synthesis, an FC aminoalkylation through a tosyliminium ion allowed the total synthesis of ( )-schefferine (Scheme 2.6) [7], which is a phenolic alkaloid isolated from Schefferomitra subaequalis, a liana climber found on rain forest trees. The known amidal 41 was treated at -78°C with 4-allyl-l,2-dimethoxybenzene (42) and BF Et O to regioselectively give 43 in 88% yield. The allylic chain of the aromatic ring was then modified to furnish alcohol 44, which after deprotection of the tosylamide was cyclized via a Mitsunobu reaction to give ( )-schefferine (46). 

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