Stille-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>. 

Oligomer 113 has been prepared in a Stille cross-coupling of 2-iodo-3-hexylthiophene 111 and bis(thrimethyl-stannyl) DTT 112 which was prepared by lithiation of the dibromide 97 followed by stannylation (Scheme 5) <2002CC2424>. 

Scheme 6.38 Scaffold decoration and modification of heterocycles using Stille cross-coupling chemistry.

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. 

Substitution at the 2-position of carbapenems by use of stannanes of the heterocycle has been explored and found to have some advantages over the conventional Stille cross-coupling which employs aryl stannanes and carbapenem triflates <00TL2995>. 

Scheme 6 Carbonylative Stille cross-coupling of vinyl halides, triflates, and sulfonyl chlorides.

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... 

A convenient route for the preparation of yne-allenes was recently described by Saalfrank et al. [19]. Products 29a/b were formed by Stille cross-coupling of allenyl bromides 27a/b with alkynylstannanes such as 28 (Scheme 14.9). Allenyl phospho-nates such as 30 were also suitable substrates in palladium-catalyzed couplings with propargylstannane 31 (Eq. 14.1). Bisstannylated acetylene 33 as alkyne component furnished the expected yne-bisallene 34 in reasonable yield, but without any diaster-eoselectivity (meso-34 (R,R)-/(S,S)-34 =50 50) (Eq. 14.2). 

In spite of these first successful results, so far Stille cross-couplings have rarely reported employing functionalized stannylated allenes such as easily available donor-substituted allene 80a or allenyl esters such as 81 (Scheme 14.19) [19, 41, 42]. A single palladium-catalyzed annulation reaction with 80b as precursor leading to an a-pyrone derivative was reported [43],... 

Scheme 2.S0. Copper(l) chloride as a promoter of Stille cross-coupling.

Stille cross-coupling and reductive N-heteroannulation steps. lodination of 1033, followed by Stille cross-coupling of the corresponding iodo derivative 1034 with the arylstannane 1035, gave the annotation precursor 1036. Reductive N-heteroannula-tion of 1036 afforded the carbazolone 1001, which was previously (99) (see Scheme 5.143) used to prepare clausenalene (90) via a Wolff-Kishner reduction followed by aromatization (659) (Scheme 5.155). 

Although the fate of the zinc ligands was not unambiguously ascertained, it appeared clearly that palladium to zinc transmetallation occurred prior to cyclization. Indeed, palla-dium-ene reactions are known but generally require higher temperatures and, when run in association with a subsequent Stille cross-coupling, trans- 1,2-disubstituted cyclopentanes were generated (equation 81)115,116. 

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... 

R. J. K. Efficient and selective Stille cross-coupling of benzylic and allylic bromides using bromobis (triphenylphosphine) (N-sucdnimi-de)Pd(II). Tetrahedron Lett. 2004, 45, 461—465. 

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