Quinolines, Claisen rearrangements

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]. 

Treatment of the 2-pyrrolyl allyl thioether (498) with acetic anhydride and quinoline at 170 °C (or in A jV-dimethylaniline at ca. 100 °C) results in a thio-Claisen rearrangement to give the 5-(3-allyl-2-pyrrolyl) thioacetate (499), whilst peracid oxidation of (498) produces the non-rearranged sulfone in low yield and Raney nickel reduction of (498) yields 3-propylpyrrole (78CJC221). The polyphosphoric acid-catalyzed cyclization of (2-pyrrolylthio) acetic acid (501 R = R = H) somewhat unexpectedly yields (502) via the Spiro intermediate, instead of forming the expected oxothiolane (500), which can be obtained by a Dieckmann cyclization of ethyl (3-ethoxycarbonyl-2-pyrrolylthio) acetate (501 R = Et, R = C02Et) (B-77MI30506). 

Amino-Claisen rearrangement of propargylamino-cyclohexenone and cyclopentenone is reported to proceed with ring closure to quinoline and pyridine derivatives (equation 82). The isomeric 2-propynylenaminone gave an indolone in good yield118 (equation 83). 

A seleno-Claisen rearrangement was utilized to prepare dihydrobenzo[ ]selenophenes <2003SC2161>. Heating selenide 130 in quinoline produced the dihydrobenzo[, ]selenophene 131 after cyclization of the selenophenol Claisen product (Equation 24). 

The Claisen rearrangement of allyl ethers in the quinoline series is thus seen to be unusually fast, affording high yields of products. In no case has migration of the allyl side-chain to the benzenoid ring been observed. Migrations to the nitrogen atom and to the alkyl side-chain proceed by concurrent rather than consecutive paths. 

Thio-Claisen rearrangement of quinoline derivatives 79PS(7)69. 

The alkaloids from Ravenia spectabilis and Flindersia ifflaiana exhibit an interesting structural variation within the quinoline group and some evidence has been presented for their genesis via biological Claisen rearrangements. ... 

Alkylation of the sodium salt of 152 with allyl bromide in DMSO afforded the 3-S-allyl 160 (R = H), which underwent a thio-Claisen rearrangement in the presence of p-toluenesulfonic acid to give 2-allyl-3-mercapto 161 (R = H) that cyclized partially during purification to hexahydrothiophene 162 (R = H). Alternatively, acetylation of 161 (R = H) gave 163, which cyclized on heating in quinoline to afford 162 (R = H). Similarly, 2-butenyl 160 (R = Me) gave 161 (R = Me) but the... 

Dimethoxy-2(lH)-quinolines (235), which are key intermediates for the synthesis of antimalarial drugs, have been prepared in poor to moderate yields by intramolecular Wittig reaction of the salts (234). A combination of Wittig olefination and Claisen rearrangement of (2-hydroxy-4-prenyloxy)phenyl carbonyl compounds (236) has been used in a one-pot synthesis of 2, 3, 3 -trimethyl-2, 3 -dihydroangelicins (237). ... 

The occurrence of (1,1-dimethylallyl)- and (l,2-dimethylallyl)quinoline derivatives in Flindersia and Ravenia species and the isolation of the prenyl ether 261 from Ravenia (Section V,B) suggested that the biosynthesis of this group of alkaloids might proceed via Claisen and abnormal Claisen rearrangements as in the synthetic route (Scheme 22, Section V, B). 

Scheme 4 Sequential Claisen and aza-Claisen rearrangements on the indolo[2,3-i)]quinoline system [37]...

Other examples of retro-Claisen rearrangement were observed in the aromatic quinoline series [30] and with bicychc systems [31, 32]. Some specific cases have been predicted by calculations to be endothermic [33, 34]. 

The thio-Claisen rearrangement of propargyl 4-quinolyl sulphide (566) gives 2-methylthieno[3,2 c]quinoline (567) in high yield. By allowing (552) to react with hydrazine, followed by treatment with ethyl orthoformate, (568) was obtained, which upon treatment with base in ethylene... 

Thermolysis of aryl allyl selenides in quinoline leads to a mixture of (Cy5) and (Cy6) compounds, paralleling the results obtained in the thio-Claisen rearrangement. These compounds may arise by intramolecular free radical addition but, as discussed in Section 4.C for the thio-Claisen rearrangement, other pathways must be considered. 

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