Cyclization intramolecular Heck reaction, 2-halo

Intramolecular Heck reactions have frequently been used for the synthesis of cyclopen-tanoid structures. In nearly all cases reported so far, the ring closure occurs as a 5-exo process (for an exception, see Table 4, entry 6), for which 2-halo-l,6-heptadienes and related compounds are the appropriate starting materials. In some cases, however, these substrates cyclize by a 6-endo mode to give cyclohexane derivatives (see Sect. IV.2.2.1.B.V). 

In their studies toward the total synthesis of Taxol , Danishefsky and co-workers have focused their attention on the formation of eight-membered rings by an intramolecular Heck reaction proceeding by an -exo-trig cyclization of a 2-halo-1,8-decadiene system (Scheme 19, Table 14). 

The Mori-Ban indole synthesis is referred to the intramolecular version of the Heck reaction applied to synthesis indoles. The cyclization of o-halo-A-allylanilines to indoles is a general and efficient methodology. For... 

Cobalt catalysts were studied by Oshima and co-workers in cyclization reactions in 2002. By using the cobalt complex [CoCl2(dppb)] as the catalyst and assisted by Me3SiCH2MgCl, the intramolecular Heck-type cyclization reactions of 6-halo-l-hexenes proceeded via a radical process to provide the corresponding tetrahydrofurans in good yields. Allyl-o-halogenophenols were tested under identical conditions and gave the desired dihy-drobenzofurans in low to excellent yields (Scheme 2.41). 

Heck indole synthesis, and Hegedus-Mori-Heckreaction, in general contains at least two types of reactions for indole derivatives. They are the palladium (n) complex-catalyzed oxidative A -heterocyclization of o-allylaniline (developed in 1976) or o-aminostyrenes (reported in 1978) and the palladium-catalyzed intramolecular cyclization of o-halo N-allylaniline (reported in 1980) the latter preparation is also referred to as the Hegedus cyclization. ... 

---