1,3-diene intermolecular hydroamination

In order to find a suitable catalyst for intermolecular hydroaminations of 1,3-dienes, several metal sources were screened for the reaction of diene la (4 equiv) with carbamate 2a, and Bi(OTf)3 gave promising results [21, 22], The optimization studies using Bi(OTf)3 are summarized in Table 1 and show that 10 mol% of... 

Table 5 Intermolecular hydroamination of various 1,3-dienes with carbamate 2d...

The intermolecular hydroamination of alkynes, catalysed by the aquapalladium complex [(dppe)Pd(H20)2](0Tf)2, has been reported. The reaction is believed to proceed through the equilibrium between the hydroxopalladium and the amidopalladium complexes, followed by aminopalladation of alkynes.76 Regioselective 1,2-diamination of 1,3-dienes by dialkylureas, catalysed by (MeCN)2PdCl2 in the presence of 1 equiv. of / -benzoquinone, has been developed as a highly efficient method.77... 

Organolanthanide-catalyzed intermolecular hydrophosphination is a more facile process than intermolecular hydroamination. The reaction of alkynes, dienes, and activated alkenes with diphenylphosphine was achieved utilizing the ytterbium imine complex 9 (Fig. 8) as catalyst [185-188]. Unsymmetric internal alkynes react regioselectively, presumably due to an aryl-directing effect (48) [186]. 

While intermolecular hydroamination of simple alkenes remains a great challenge as of now, addition of amines to alkynes, allenes, and dienes proceeds more easily. However, the addition of an amine to a polyene moiety may not necessary result in the formation of a new stereocenter, if an imine is generated (Scheme 11.18). 

Scheme 11.18 Intermolecular hydroamination of alkynes, allenes, and dienes.

The use of carbamates as the nucleophile allowed extension of the method to the gold-cataWzed intermolecular hydroamination of conjugated dienes at room temperature. The reaction took place regioselectively as 1,2-addition at the less substituted double bond. 

The hydroamination of cycloheptatriene has also been reported (Equation 16.83). Although the mechanism of this reaction has not been revealed, it is likely to be related to the mechanism of the palladium-catalyzed hydroamination of dienes. TTie overall transformation must involve two hydroaminations one intermolecular hydroamination of the triene unit and one intramolecular hydroamination of the resulting diene. 

Mild and selective 1 1 reactions of amines with 1,3-dienes without telomer-ization are still limited. The recently reported bismuth-catalyzed intermolecular hydroamination with various amides (carbamates, sulfonamides, and carboxamides) to produce allylic amines in good yields is a good example of such a reaction (Equation 56 and Scheme 11.4) [80]. Some additives are necessary to optimize the reaction conditions. Cyclic and acyclic dienes were tested. The isomer ratio (1,2-adduct versus 1,4-adduct) depended on the nature of the dienes. 

In the hydroamination of unsaturated carbon-carbon bonds, gold catalysts play an important role. Intermolecular hydroamination of alkenes [177], 1,3-dienes [204], terminal and internal alkynes [205], and allenes [206] are known to proceed smoothly in the presence of PhsP AufI) or AuCls catalyst. In addition, amino olefins also efficiently undergo intramolecular hydroamination using similar gold catalysts. He and coworkers have developed the catalytic cycloaddition of tosylated amino olefins [207], A representative example is shown in Scheme 18.35. When N-tosylated y-amino olefin (97) is exposed to a mixture of PhsP AuCl and AgOTf (5 mol% each) in toluene at 85 °C, pyrrolidine (98) is obtained in 96% yield. The gold(I)-catalyzed intramolecular hydroamination is applicable to N-alkenyl carbamates [208], N-alkenyl carboxamides [209], and N-alkenyl ureas [210], The use of microwave irradiation results in completing the hydroamination in a much shorter time than that required under thermal reaction conditions [211], The... 

Multiple efficient catalysts were reported for the intramolecular process, while the intermolecular process has been studied predominantly for alkynes. The reactivity of the unsaturated fragment decreases in the order alkyne > allene diene > vinyl arene unactivated alkene with the intermolecular hydroamination of simple alkenes representing the most difficult transformation. The hydroamination of all types of carbon-carbon unsaturated fragments will be covered in this chapter. 

The Bi(OTf)3-Cu(CH3CN)4PF6 system has been reported to promote efficiently an intermolecular 1 1 hydroamination of 1,3-dienes R1CH=CHCH=CHR2 with various carbamates, sulfonamides, and carboxamides to afford allylic amines in Markovnikov... 

The intermolecular addition of carbamates to 1,3-dienes (equation 147) under mild conditions has been described as well. The hydrothiolation of 1,3-dienes has also been reported. " Other related conjugate additions can be performed over methylenecyclopropanes (equation 148) with sulfonamides and the resulting product cyclizes by a second hydroamination of an olefin, finally yielding cyclic sulfonamides. This behavior is reproduced in a similar reaction for the ring opening of vinylcyclopropanes with sulfonamides. One more example in this group of reactions is the synthesis of dUiydrobenzofurans from aryl-allyl ethers. ... 

Type 4 metallocene complexes catalyze the regioselective mtermolecular addition of primary amines to acetylenic, olefinic, and diene substrates at rates which are = 1/1000 those of the most rapid intramolecular analogues [165]. Variants such as the intramolecular hydroamination/cyclization of aminoallenes [166] and the intra- and intermolecular tandem C-N and C-C bond-forming processes of aminodialkenes, aminodialkynes, aminoallenynes, and aminoalkynes [167] were applied as new regio- and stereoselective approaches to naturally occurring alkaloids. For example, bicyclic pyrrolizidine intermediate E... 

The hydroamination of 1,3-dienes has been known for many years, but these reactions have often generated mixtures of products. More recently, the intermolecular and intramolecular hydroamination of dienes has been reported with lanthanide and palladium catalysts to generate allylic amines in high yields. These reactions have also occurred with high enantioselectivity in some cases. 

Zhou J, Hartwig JF. Intermolecular, catalytic asymmetric hydroamination of bicychc alkenes and dienes in high yield and enantioselectivity. J. Am. Chem. Soc. 2008 130(37) 12220-12221. 

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