Intramolecular, addition rearrangement

The mechanism of the indolization of aniline 5 with methylthio-2-propanone 6 is illustrated below. Aniline 5 reacts with f-BuOCl to provide A-chloroaniline 9. This chloroaniline 9 reacts with sulfide 6 to yield azasulfonium salt 10. Deprotonation of the carbon atom adjacent to the sulfur provides the ylide 11. Intramolecular attack of the nucleophilic portion of the ylide 11 in a Sommelet-Hauser type rearrangement produces 12. Proton transfer and re-aromatization leads to 13 after which intramolecular addition of the amine to the carbonyl function generates the carbinolamine 14. Dehydration of 14 by prototropic rearrangement eventually furnishes the indole 8. 

A stannanimine has been prepared from a highly hindered diazastanny-lene and 2,6-diisopropylphenylazide.88 The stannanimine is stable in solution at -30°C, but rearranges within two weeks by the intramolecular addition of a C—H bond of one of the isopropyl groups across the Sn=N bond. 

The intramolecular addition of alkynyl-substituted a-diazoketones is catalyzed by Rh2(OAc)4 to give transient cyclopropenes, which spontaneously rearrange to vinylogous a-keto carbene intermediates for further carbon-skeleton transformations [54]. 

Preferential reduction of a nitro group in the presence of a carbonyl group in 4-nitroacetophenone ISD, intramolecular rearrangements of o-nitro-benzanilides 32) intramolecular cyclizations of o-nitro-ferf-anilines to benzimidazol-1-oxides 153,154) cyclizations of acylated 2-nitrodiphenylamines to phenazine-l-oxides i ), intramolecular additions of nitro groups to double bonds 156) remarkably ef-... 

High levels of asymmetric induction can be achieved intramolecularly if the substrate functionality and the heteroatom ligand are contained in the same molecule. Chiral amido(a]kyl)cuprates derived from allylic carbamates [(RCH= CHCH20C(0)NR )CuR undergo intramolecular allylic rearrangements with excellent enantioselectivities (R = Me, n-Bu, Ph 82-95% ee) [216]. Similarly, chiral alkoxy(alkyl)cuprates (R OCuRLi) derived from enoates prepared from the unsaturated acids and trans-l,2-cyclohexanediol undergo intramolecular conjugate additions with excellent diasteroselectivities (90% ds) [217]. 

The intramolecular addition of silyl radicals to aromatic rings has also attracted some attention. Early work on the silyl radical obtained by the reaction of silanes 41 with thermally generated t-BuO radicals at 135 °C showed the formation of rearranged products only for = 3 or 4, whereas for = 1, 2, 5, and 6 no rearrangement took place [20],... 

An unusual intramolecular addition of one ortho C-H bond of a phenyl substituent across the C3=C4 bond in 20 (Scheme 3.33) is observed on thermolysis of 20 in CHCI3 [7]. A similar complex is also formed when the corresponding dppm complex is generated in situ from [Cl(dppm)2Ru-C = C-C = C-C(Ph)20SiMe3] and HBF4 in CH2CI2 [30, 31]. This transformation is actually the parent of the later commonly observed allenylidene to indenylidene intramolecular rearrangement. 

The acid-mediated intramolecular addition of the azide to the ketone proceeds by way of addition followed by a pinacol-type rearrangement, to give the amide 12. The regioselectivity of the bond migration is remarkable. Reduction of the amide then gave 3. 

The ethoxycarbocation intermediate (363) produced by the action of acid on the cyclobutenedione monoacetal (362) has been found to react with bis(trimethylsilyl)-acetylene to afford a 2-methylenecyclopent-4-ene-l,3-dione derivative (365). The authors426 proposed that the rearrangement results from an unprecedented cationic 1,2-silyl migration on the alkynylsilane, subsequent ring expansion via a vinyl cation intermediate (364), and re-closure by intramolecular addition of an acyl cation to a silylallene in a 5-exo-trig mode (see Scheme 90). 

The rearrangements of silylenes, like those of carbenes, can involve H shifts and the shifts of C—C bonds (intramolecular insertion and ring expansion) or cyclization by intramolecular addition to C=C jr-bonds5. The mechanism discovered by Barton for... 

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