Stille reaction/cross-coupling

Despite being activated by the nitrogen atom, 2-chloroquinoline (25) is still a poor substrate for the Stille cross-coupling reactions, though yields are usually improved under Negishi conditions. For instance, the coupling of... 

Stille cross coupling reactions usually proceed under mild neutral conditions. 2-Substituted thiazoUnes can be obtained by the cross coupling reaction of 2-bromothiazolines with various tributylstannyl compounds. Previous attempts at a palladium mediated coupling of 2-trimethylstannylthiazoUne led to only decomposition of the substrate <96TL4857>. 

Palladium(0)-catalyzed coupling reactions - i. e. the Heck and Sonogashira reactions, the carbonylative coupling reactions, the Suzuki and Stille cross-coupling reactions, and allylic substitutions (Fig. 11.1) - have enabled the formation of many kinds of carbon-carbon attachments that were previously very difficult to make. These reactions are usually robust and occur in the presence of a wide variety of functional groups. The reactions are, furthermore, autocatalytic (i.e. the substrate regenerates the required oxidation state of the palladium) and a vast number of different ligands can be used to fine-tune the reactivity and selectivity of the reactions. 

The heteroaromatic stannanes undergo the normal electrophilic substitution reactions of their protic precursors, and often to an enhanced degree. They are often prepared with the aim of a subsequent Stille cross-coupling reaction, and oligothiophenes with potentially useful optical and electron properties have been prepared by coupling between stannyl- and bromo-thiophenes, for example, Equation (63).204... 

Similarly, the Migita-Kosugi-Stille cross-coupling reaction (Equation (115)) is important in organic synthesis and has IS 190 302 303, 1... 

Making use of an earlier finding that Sn compounds containing Sn—CH2R bonds were suitable for Stille cross-coupling reactions,one-pot C—H activation and cross-coupling products were isolated in modest yields (21 % from MeOBu and 5 % from n-CsH 12 based on Sn amide) as shown in Equation (9.13) (R CH2OBU or n-CsHn). ... 

Chamoin, S. Houldsworth, S. Snieckus, V. The Stille Cross Coupling Reactions on Solid Support. Link to Solution Phase Directed ortho Metala-tion. An Ester Linker Approach to Styryl, Biaryl and Heterobiaryl Carboxylic Acids, Tetrahedron Lett. 1998, 39, 4175-4178. 

Samuelsson, L. and LangstrOm, B., Synthesis of l (2 deoxy-2 -fluoro-(3-D-arabinofuranosyl)-[Me thy l-nc]Thymine ([nc]Fmau) via a Stille cross-coupling reaction with [nc]Methyl Iodide, J. Labelled Compd ... 

Carreira and co-workers have also extended the scope of aldehydes that may be utilized in catalytic addition reactions to include stannylpropenal 108 as a substrate (Table 8B2.12, Entry 7). The adduct produced from the aldol addition of 105 is isolated with 92% ee and serves as a useful building block, as it is amenable for further synthetic elaboration (Scheme 8B2.9). Thus, vinylstannane 109 is a substrate for Stille cross-coupling reactions to give a diverse family of protected acetoacetate adducts 110. Following deprotection of the masked keto ester, the corresponding hydroxy keto ester 111 may be converted to either the syn or anti skipped polyols 112 or 113. A recent total synthesis of macrolactin A by Carreira and co-workers utilizes aldol... 

The Stille cross-coupling reactions of thienyl-3-carbamate 115 with o-formyl (trimethylstannyl)pyridines 118-120 (1994JHC1161) or acetal 121 (1992MI3, 1994JHC1161, 1994JOMC127) afford a series of isomeric thienonaphthyridines 122-125. The addition of CuO to the reaction mixture leads to an increase in rate (1993JOMC127). 

Pyridine ring construction according to strategy P is based on the one-step formation of the C(4)-N(5) and C(7)-C(7a) bonds. For example, this approach provides the basis for the synthesis of the simplest isomeric dithienopyridines (1988CS281). The Stille cross-coupling reaction of 2-tributylstannyl-3-thiophene-carbaldehyde (256) with thienylcarbamates 115, 257, and 258 affords the target compounds 259-261, respectively, in different yields. 

The one-pot Stille cross-coupling reaction of compound 256 produced all four isomeric thieno[3,2-c]naphthyridines (1994JHC11). The stepwise formation of the C(7)-C(7a) and C(4)-N(5) bonds of the thieno[3,2-c]pyridine system can be considered as a modification of the above-described approaches. For example, aldehyde 256 reacts with arene 265 to give 266 reduction of its nitro group is accompanied by cyclization to form thieno[3,2-c]isoquinoline A-oxide (267) (1990JHC1127). 

Palladium forms with both silylenes 83 and 84 silylene-bridged dinuclear complexes. The dinuclear Pd(0) complex 110 (R = Ph) was found to be active in Suzuki and Stille cross-coupling reactions <2001CC2372, 2002JOM141>. NMR investigations indicate that also homoleptic silylene complexes of Pd(0) such as Pd(83)(, [Pd(83)2]2, and Pd(84)4 exist these complexes are, however, very labile <2002JOM141>. 

Stille coupling between suitable 6-chloropurines and aryl(tributyl)tin afforded 6-arylpurines with a variety of substituents in the 9-position which were screened for antimycobacterial activity <02JMCI383>. The Stille cross-coupling reactions of 1,4- and l,3-bis(trialkylstannyl)benzenes with 9-benzyl-6-chloropurine gave 1,4- and l,3-bis(purin-6-yl)benzenes and 4-(purin-9-yl)benzenes <02T7431>. 

Thus, an efficient and convergent total synthesis of ( )-isocembrene has been accomplished in seven steps from the known geranylacetone through an intramolecular Stille cross-coupling reaction. The strategy is of great potential for the divergent synthesis of complex cembrane-type diterpenoids such as cembrene-C and sarcophytols. 

In the study of catalytic, dienolate addition reactions, the use of stannyl prope-nal 50 as a substrate in aldol methodology has been introduced (Scheme 8-4). The adduct 51 produced from the process is isolated in 92% ee and, importantly, serves as a useful building block for subsequent synthetic elaboration. It is amenable for further manipulations such as Stille cross-coupling reactions to give a diverse family of protected acetoacetate adducts 52. 

The Stille cross-coupling reaction between various heteroarylstannanes and ring-brominated benzylphosphonates (107) has been used to prepare heterobiaryl phosphonates 108. A key step in the synthesis of individual optical isomers of 2-hydroxymethyl-4-[3-(diethoxyphosphinyl)propyl]-5-alkylpiperazines 109 as CPP analogues is the alkylation of protected 5-alkyl-2-hydroxymethylpiperazines with (3-bromopropyl)phosphonate (Scheme 5). Compound 110, a new member... 

Pd is also a potential contaminant and Nobile and coworkers recently employed a polymer-supported palladium complex (Pd-pol, Figure 5.3.1), obtained by copolymerization of Pd(AAEMA)2 with ethyl methacrylate and ethylenene glycol dimethacrylate (AAEMA is the deprotonated form of 2-(acetoacetoxy)ethyl methacrylate), as a catalyst in Stille cross-coupling reactions [Equation (5.3.14)]. The reaction can be performed in air without any activating ligand and with non-dried solvents. The catalyst can be recycled several times. 

---