5.6.7.8- tetrahydroisoquinoline alkene

Among the simplest syntheses of this type are those of tetrahydro-quinolines or -iso-quinolines based on Friedel-Crafts cyclizations. The use of side-chain halides is shown by the synthesis of 1,2,3,4-tetrahydroisoquinolines (158) (71CC799), and of 3,4-dihydroquinol-2-ones (159) (27CB858). Electrophilic carbon atoms can be developed from secondary or tertiary alcohols, or from alkenes or alkynes. In the synthesis of the tetrahydroisoquinoline... 

Palladium chemistry has been used in the synthesis of tetrahydroisoquinolines. Different combinations of iodoaryl-amine-alkene can be used in these multicomponent reactions. For example, the metal-mediated o-alkylated/alkenyl-ation and intramolecular aza-Michael reaction (Scheme 109) give moderate yields of heterocycle <2004TL6903>, whereas the palladium-catalyzed allene insertion-nucleophilic incorporation-Michael addition cascade (Equation 172) produces good yields of tetrahydroisoquinolines in 15 examples <2003TL7445> with further examples producing tetrahydroquinolines (Scheme 110) <2000TL7125>. 

The next three chapters are by Inoue and Mori, Albini, and Rossi, and deal with alkene photoisomerization reactions, the modification of benzylic positions and photochemical aromatic substitution reactions. (E)-2-cyclo-heptenone is produced upon irradiation of the Z-isomer at — 50 °C and can be trapped by cyclopentadiene to afford the adduct 13 [13]. Benzyl-substituted dihydroisoquinolinium derivatives can be used for the photochemical synthesis of tetrahydroisoquinolines. The corresponding... 

SCHEME 5.2 Oxygen transfer to alkenes mediated by a oxaziridinium salt derived from tetrahydroisoquinoline. 

A chiral Ir(I) catalyst derived from the amino-(2,2 -biphenoxy)phosphine 37 promotes the synthesis of optically active 3-amino-l-alkenes from 2-alkenols, which are activated by (Eto)5Nb/ l-Vinyl-l,2,3,4-tetrahydroisoquinolines are obtained in good yields in the Pd-catalyzed process. Enantioselectivity is induced by the atropisomeric 38. ... 

As introduced in Section 2.2.4, monobenzylic alcohols are inherently poor substrates for reduction using NaBH TFA. However, notable exceptions have been discovered and this tactic has a synthetic niche as illustrated with reduction products 101-105. Diastereo-selective introduction of deuterium was reported in the studies involving tetrahydroisoquinoline 102.89 Note that alkene formation from the carbocation intermediates... 

Frequently seen are Parham cyclizations onto alkene side chains. For example, bromoalkene 39 undergoes cyclization and electrophilic trapping to afford 40. A series of allyl 2-lithioaryl ethers undergo a tandem Parham cyclization-y-elimination to afford 2-cyclopropylphenols, e.g., 41- 42. Intramolecular carbolithiation reactions of alkenes have led to 2-azabenzonorbomanes and tetrahydroisoquinolines. Similarly, carbolithia-tions of alkyne and allene side chains have been reported. Thus, both 43 and 45 undergo iodine-lithium exchange and cyclization to provide benzofuran 44 and fiiropyridine 46, respectively. 

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