Smiles rearrangement transition state

The conversions 65 —69 and 70 —> 72 can proceed by several pathways. An ionization of the nucleophilic function XH in aniline 65 may lead to final product 69 via the transition state 67. On the other hand, a preliminary 65 -> 66 ionization is not always required, and the rearrangement may occur in a concerted fashion through transition state 68. Besides, in some systems another possibility can be realized when a stabilized intermediate 71 can participate in the rearrangement103. Very voluminous information about the Smiles rearrangement has been summarized in detail103-107. 

Simmons-Smith cyclopropanation, 456 Simmons-Smith reaction, 455 six-centered transition state, 264 Smiles-type rearrangement, 7 SOCI2, 19, 159 sodium azide, 365, 375 sodium borohydride, 416 sodium hexamethyldisilazide, 290 sodium hydride, 372, 375. 383 sodium in liquid ammonia, 440 sodium iodide, 379 sodium phenylselenide, 458 sodium trifluoroethoxide, 447 solid phase synthesis, 25 Sonogashira conditions, 409 Sonogashira coupling, 411 spartadienedione, 144 spontaneous csdodimerization, 23 S-shaped and C-shaped diastereomers, 83 stainless steel reactor, 283... 

Smiles processes involving three-membered cyclic transition states are much less frequent under ionic conditions.However, similar Truce-Smiles processes under radical conditions are well documented. Known as neophilic rearrangements, they lead to efficient carbon-aryl bond formation with frequent extrusion of small molecules such as sulfur dioxide. These Smiles-type reactions involving cyclic transition states with a small ring size will not be evaluated further in this chapter. 

Ito and coworkers discovered a nniqne Trnce-Smiles rearrangement of the substituted anilide intermediate 16 upon exposure to LDA. When 16 was subjected to an oxidative process (LDA, THE, Oj, -70°C), the rearranged product 17 was obtained in 75% yield instead of the desired oxidation product. Their proposed transition state geometry (18) is depicted in the box in Figure 18.2 [11]. 

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