Diels-Alder reactions of indoles

Table 4.13 Photoinduced Diels-Alder reactions of indoles 64 and dienes 61-63 with sensitizers 59 and 65...

Some other ring expansions involving the intramolecular amino Claisen rearrangement of vinylarylaziridine [ 123], the Diels-Alder reaction of indoles with acetylene derivative [124-127] and the dibromocarbene insertion into quinoline enol ethers [ 128] have been used to prepare 1-benzazepines. On the other hand, treatment of 3-chloro-3-phenyl-l,2,3,4,5,6-hexahydro-l-benz-azocin-2-ones with piperidine causes a ring contraction to give 2-phenyl-2-(l-piperidinylcarbonyl)-2,3,4,5-tetrahydro-l//-l-bcnzazepines in an excellent yield [23]. 

Diels-Alder reaction of indole-2,3-quinodimethanes, 164-169 of pyrrole-2,3-quinodimethanes, 85-87 of vinylindoles, 159 -164 of vinylpyrroles, 79, 84-85 N.N-dihexyl 2-phenylindole-3-acetamide, procedure for. 62... 

Gieseler, A., Steckhan, E., Wiest, O., and Knoch, F. (1991) Photochemically induced radical cation Diels-Alder reaction of indole and electron-rich dienes. Journal of Organic Chemistry, 56, 1405-1411. 

The electron transfer activates molecule and enables the cycloaddition process. The kinetics of these reactions is well documented much less information is on the nature of regio- and stereoselectivity. The stepwise mechanism was proposed for the electron-transfer-catalysed Diels-Alder reaction of indole and 1,3-cyclohexadiene catalysed by fn s(4-bromophenyl)aminium hexachloroantimonate in dichloromethane at 0°C in the presence of NaHC03 and CH3COCI (Scheme 3).64... 

Figure 4 13C KIEs for the radical-cation catalysed Diels-Alder reaction of indole with cyclohexadiene.

Although the Diels-Alder reaction of indoles had been investigated... 

Isolated in the for of the ketone after hydrolysis of the silyl enol ether Scheme 7.2. Diels-Alder reaction of indole 7 with various dienes 8. 

A study of the stereoselectivity of the radical-cation Diels-Alder reaction of indole with the diene 139 gave a mixture of both cis and trans adducts. This lack of stereospecificity is consistent with other evidence that the radical-cation cycloaddition is non-concerted. <93TL6391>... 

Nucleophilic addition, 1,3-dipolar cycloaddition, and Diels-Alder reactions of indoles substituted at the 2- or 3-position with electron-withdrawing groups (NO2, PhS02) 05COC1493. 

The prominence of the Diels-Alder reaction of quino-2,3-dimethanes (also known as ortfto-quinodimelhanes and < rt/j( -xylylenes) has been established for nearly six decades since the seminal work by Cava [1,2], Several excellent reviews are available [3-7]. The logical extension of this chemistry to the synthesis and Diels-Alder reactions of indole-2,3-quinodimethanes (2,3-dimethylene-2,3-dihy-dro-l/7-indoles) has been recognized as an efficient route to indoles, carbazoles, and related fused indoles [8],... 

Beyond Diels-Alder reactions of indole-2,4-qui-nodimethanes to construct indoles, there is a wealth of indole ring synthesis involving Diels-Alder cycloadditions and electrocyclizations that do not begin with an indole or indolone. Indeed, a number of ingenious indole ring syntheses starting from scratch are known. 

Z. Chen, B. Wang, Z. Wang, G. Zhu, J. Sun, Angew. Chem. Int. Ed. 2013, 52, 2027-2031. Complex bioactive alkaloid-type polycycles through efficient catalytic asymmetric multicomponent aza-Diels-Alder reaction of indoles with oxetane as directing group. 

Scheme 35 Asymmetric [4+2] inverse-electron-demand aza-Diels-Alder reaction of indoles with...

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