Allylamines hydroboration

Addition reactions to olefins can be used both for the construction and for the functionalization of molecules. Accordingly, chiral catalysts have been developed for many different types of reactions, often with very high enantioselectiv-ity. Unfortunately, most either have a narrow synthetic scope or are not yet developed for immediate industrial application due to insufficient activities and/ or productivities. These reactions include hydrocarbonylation [Ilf], hydrosilyla-tion [12 i], hydroboration [12j], hydrocyanation [12 k], Michael addition [11 g, 121, 12 m], Diels-Alder reaction [11 h, 12n] and the insertion of carbenes in C-H bonds [Hi, 12p, 12q, 38], Cyclopropanation [Hi, 12p, 12q] and the isomerization of allylamines [12 s] are already used commercially for the manufacture of Cilastatin (one of the first industrial processes) [12 r], and citronellol and menthol (presently the second largest enantioselective process) [12t] respectively. 

As 4-atom fragments, allylamines are often used for the synthesis of 1,2-azaborolidines, 1,2-azoniaboratolidines, 1,2-azaboroles, and 1,2-azoniaboratoles. 1,2-Azaborolidines are generally formed if borane-amine adducts are thermally burdened in the presence of alkyl-, allyl-, and diallyl amines. These reactions can also be described as hydroborations of diallyl compounds (Equations (22) and (23)) <70ZOB1528,76IOC2803>. 

Prior chapters have covered the use of transition metals in asymmetric hydrogenations ( 6.2 and 7.1), hydroborations ( 7.3), hydrosilylations and hydro-cyanations ( 6.3, 6.4, 7.4 and 7.5), cyclopropanations ( 7.19), aldol reactions ( 6.11), allylations of carbanions ( 5.3.2), and some sigmatropic rearrangements ( 10.3). This chapter covers other reactions catalyzed by transition metal complexes including coupling of organometallic reagents with vinyl, aryl or allyl derivatives, Heck reactions allylamine isomerizations, some allylation reactions, car-bene insertions into C-H bonds and Pauson-Khand reactions. 

The excellent syn selectivity of chiral allylamine derivatives, using catalyzed hydroboration with 9-BBN and borane-THF complex, can be explained by the following reactive conformations (Fig. 5.3). 

Table 8.1 Diastereoselectivities for hydroboration-oxidation of allylamine derivatives [10]...

The Suzuki-Miyaura reaction [26] is a very reliable method for connecting the building blocks. It was of interest to apply it to allylamines in that capacity. We found that hydroboration of the vinyl group can be reliably accomplished with 9-borabicyclo[3.3.1]nonane (9-BBN), even in the presence of further disubsti-tuted double bonds, and the subsequent Suzuki-Miyaura coupling works well [27]. Several targets were addressed with these key reactions [28]. An example is... 

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