Molander coupling

Kagan-Molander coupling Sml2-mediated addition of alkyl, allyl or benzyl halides to carbonyl compounds. 232... 

Molander and Hiersemann (60) reported the preparation of the spirocyclic keto aziridine intermediate 302 in an approach to the total synthesis of (zb)-cephalotax-ine (304) via an intramolecular 1,3-dipolar cycloaddition of an azide with an electron-deficient alkene (Scheme 9.60). The required azide 301 was prepared by coupling the vinyl iodide 299 and the aryl zinc chloride 300 using a Pd(0) catalyst in the presence of fni-2-furylphosphine. Intramolecular 1,3-dipolar cycloaddition of the azido enone 301 in boiling xylene afforded the desired keto aziridine 302 in 76% yield. Hydroxylation of 302 according to Davis s procedure followed by oxidation with Dess-Martin periodinane delivered the compound 303, which was converted to the target molecule (i)-cephalotaxine (304). 

Lithium alkynyl(trialkoxy)borates have also been found suitable partners for this reaction, and have been success-fully coupled with aryl bromides, iodides, and allyl carbonates. Molander recently reported on the coupling of alkynyltrifluoroborates with aryl bromides, triflates, and chlorides in moderate yields using Pd(dppf)Gl2 as catalyst and GS2GO3 as base, in THF or water at 60... 

Another alternate to the Sonogashira coupling was reported by Blum and Molander, where sodium tetraalkynylaluminatcs were coupled with bromoazines and bromoazoles in the presence of a palladium-triphenylphosphine catalyst system. 5-Bromopyrimidine coupled with the TMS-acetylide, for example, to give the cthynylpyrimidinc in excellent yield (7.41.),59 The transmetalating reagents were prepared in situ by the reaction of the appropriate acetylene derivative with sodium aluminiumhydride. 

Several examples of intramolecular ketyl anion/unactivated olefin coupling reactions were reported by the Molander group, one of which is illustrated in equation 2884. An interesting facet of this reaction is that it is possible to further react the cyclized samarium(III) intermediate (47) with a variety of electrophiles, thereby enhancing the... 

Molander GA, Ellis N (2007) Organotrifluoroborates protected boronic acids that expand the versatility of the Suzuki coupling reaction. Acc Chem Res 40 275-286... 

Molander et al. have reported on the dianionic [4 + 3] annulation reaction of 1,4-dicarbonyl compounds with 3-iodo-2-[(trimethylsilyl)methyl]propene (4a X = I, Y = CHiSiMea) x)moted by tin(II) fluoride The extraordinary efficiency of ttiis novel stereoselective seven-member ring forming process, coupled with the simplicity of the procedure, promises to provide an expedient route to innumerable cyclic organic molecules (Scheme 9). 

KAGAN-MOLANDER SAMARIUM DIIODIDE-MEDIATED COUPLING... 

In the laboratory of G.A. Molander, a general route for the synthesis of eunicellin diterpenes was developed and was applied for the asymmetric total synthesis of deacetoxyalcyonin acetate. One of the key steps was an inramolecular NHK coupling reaction between an enol triflate and an aldehyde. The cyclopentenol product was formed in high yield as a 2 1 mixture of diastereomers. The undesired diastereomer could be transformed to the desired one using a Mitsunobu reaction. 

Related reactions Grignard reaction, Kagan-Molander samarium diiodide coupling, Nozaki-Hiyama-Kishi reaction ... 

Kaaan-Molander Samarium Diiodide-Mediated Coupling.232... 

Molander, G. A., Bernard , C. R. Suzuki-Miyaura Cross-Coupling Reactions of Potassium Alkenyltrifluoroborates. J. Org. Chem. 2002, 67, 8424-8429. 

Molander, G. A., Yun, C.-S. Cross-coupling reactions of primary alkylboronic acids with aryl triflates and aryl halides. Tetrahedron 2002, 58, 1465-1470. 

Molander, G. A., Dehmel, F. Formal Total Synthesis of Oximidine II via a Suzuki-Type Cross-Coupling Macrocyclization Employing Potassium Organotrifluoroborates. J. Am. Chem. Soc. 2004, 126, 10313-10318. 

Molander has effected a Suzuki reaction between 7-bromoindole and potassium trifluoroborates (e.g. 155) to give the corresponding coupled product 156 [163]. 

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