Cross-tandem coupling

Some of these molecules are of current interest as effective photosensitizers for biomedical applications and are employed in the photodynamic therapy of tumors and viral inhibition. Compound 142, oxobronzaphyrin, is noteworthy since it contains three distinct heterocycles and was isolated from a cross-tandem coupling reaction between a furan dipyrraldehyde and a thiophene dipyrraldehyde [184]. 

Duan et al. developed a Cu20-catalyzed synthesis of highly functionalized dihydroquinolinones through tandem oxidative cyclization of cinnamamides with benzyl hydrocarbons (Scheme 8.96). The reaction proceeds smoothly via the direct cross-dehydrogenative coupling of C(sp )-H and C(sp )-H bonds using tert-butylperoxy benzoate (TBPB) as oxidant. This is the first example... 

A tandem cyclisation/cross-coupling reaction between 6-halo-1-hexene 82 and Grignard reagents 83 is successfully catalysed by a NHC-Co catalytic system (Scheme 5.23) [23]. 

Table 2 A tandem hydrosilylation cross-coupling approach to aryl olefins...

The tandem use of asymmetric allylboration to give enantiomerically pure ho-moallyHc alcohols followed by cross-metathesis of homoallylic silyl ethers with p-substituted styrenes has been reported [120] (Eq. 19). Exclusively trans cross-coupled products were formed in 50-75% yields. 

Grigg employed organozinc chemistry to construct 3-alkylidenedihydroindoles such as 91 via a tandem Pd-catalyzed cyclization-cross coupling sequence [112]. A similar route to such compounds was reported by Luo and Wang e.g., 92 to 93 [113]. 

A methodology for the synthesis of substituted thiazolo[3,2-rz]benzimidazoles 250 from 2-propargylmercapto benzimidazole 249 was developed based on a tandem Sonogashira cross-coupling with iodoaryls and a subsequent exocyclic heterocyclization (Equation 109) <2004TL5747>. 

Ishikura et al. reported the total synthesis of ellipticine (228) starting from N-Boc indole (1256) and the vinyl bromide 1258 (719-721). This methodology involves a palladium-catalyzed, tandem cyclization-cross-coupling reaction of the indolyl borate 1257 with the vinyl bromide 1258 as the key step. Using a literature procedure, the vinyl bromide 1258 was prepared as an E/Z mixture starting from CIS- and trans-crotyl alcohol. The indolyl borate 1257 was generated in situ from... 

The 8/7-thieno[2,3-3]indole 457 was prepared by tandem cross-coupling and cyclization reactions analogously to 4/7-thieno[3,2-3]indole 358 (Scheme 37) from 3-bromothiophene <2002SL207, 20040L533>. 

SCHEME 4. Pd-catalyzed hydrozirconation-cross-coupling tandem reaction... 

SCHEME 50. Synthesis of conjugated oligoenes via an iterative hydrozirconation-cross-coupling tandem process149... 

SCFIEME 5E Synthesis of ft- and -carotenes via an iterative carboalumination-cross-coupling tandem process9... 

SCHEME 66. The Zr-catalyzed ethylzincation-Pd-catalyzed cross-coupling tandem processes... 

The 87/-thicno 2,3-/ ]indole 181 was prepared a by tandem of cross-coupling and cyclization reactions in very good yield (76%) [13] from 2-nitroboronic acid 25 and 3-bromothiophene 182 (Scheme 33) analogously to 4//-thicno 3,2-/ indolc 28 (see Scheme 33). 

Tandem cyclic carbopalladation cross-coupling process... 

Tandem radical cyclization/cross-coupling 2 Low-valent Fe 2.1.3... 

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