Cross-coupling thermal

The Suzuki cross coupling reaction features in a synthesis of 4-arylcoumarins from the 4-halogeno derivatives c96JCS(Pl)2591> and in a route to the thieno[3,4-c]coumarin (8) from which coumarin 3,4-quinodimethane (9) can be thermally generated <96T3117>. 

The 5-triflate of 1,3-dioxin undergoes a variety of facile Pd-catalysed cross coupling reactions affording 5-substituted 1,3-dioxins from which acrolein can be thermally generated in high yield by a retrocycloaddition. In particular, this approach leads to a new class of 2-acylacroleins (Scheme 61) <00T10275>. 

In addition, arylthiophene 70 was obtained by a one-pot Suzuki coupling of p-methoxyiodobenzene and 3-bromothiophene via an in situ boronate formation using one equivalent of the thermally stable diborane 69 [55], This method avoids the isolation of boronic acids and is advantageous when base-sensitive groups such as aldehyde, nitriles and esters are present. However, the cross-coupling yields are low when both aryl halides are electron-poor because of competitive homocoupling during the reaction. 

The Liebeskind group cross-coupled 4-chloro-2-cyclobutenone 69 with 2-tribuylstannyl-benzothiazole to synthesize a-pyridone-based azaheteroaromatics [48], The adduct 70 underwent a thermal rearrangement to afford a transient vinylketene 71, which then intramolecularly cyclized onto the C—N double bond of benzothiazole, giving rise to thiazolo[3,2-a]pyridin-5-one 72. In another case, 2-acetyl-4-trimethylstannylthizaole (73) was coupled with an acid chloride 74 to form the desired ketone 75 [49]. 

The stannylboration of alkynes was followed by cross-coupling of the G-Sn bond in the synthesis of stereodefined 1-alkenylboron compounds 143 (Equation (48)).261 There was a large accelerating effect of boryl substituents on thermal ring closing to the methylene cyclobutenes at 140 °G. 

Coefficients Lqq and Lt] are associated with the thermal conductivity k and the mutual dififusivity D, respectively, while the cross coefficients Liq and Lqi define the coupling. Thermal conductivity (k) is related to Lqq by k = LqJT, while the thermal diffusion coefficient is related to Liq by Liq = pDTi. Tables 7.9 and 7.10 show the values of the phenomenological cofficients Lq for the ternary mixture of toluene (l)-chlorobenzene (2)-bromobenzene (3) at 298.15 and 308.15 K. 

A mixture of two different alkylcopper compounds can, when thermally decomposed, give rise to cross-coupled dimers (37, 299) and cross-... 

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