Morpholine, hydroamination with

Yamamoto has also demonstrated the intermolecular hydroamination of mono-substituted arylallenes with morpholine [40]. For example, treatment of l-p-tolyl-1,2-propadiene with morpholine and a catalytic 1 1 mixture of [PPh2(o-tolyl)]AuCl and AgOTf in toluene at 80 °C for 24h led to isolation of the allylic amine 56 in 83% yield as a single regio- and stereo-isomer (Eq. (11.31)). 1-Alkylallenes, 1,1-, and 1,3-disubstituted allenes also underwent gold(I)[Pg.450]

Hydroamination of activated alkenes has been reported with complexes 91-93 (Fig. 2.15). For example, 91 catalyses the hydroamination of methacrylonitrile (X = CN in Scheme 2.13) by a range of secondary amines (morpholine, thiomorpholine, piperidine, iV-methylpiperazine or aniline) in good to excellent conversions (67-99%) and anfi-Markovnikov regioselectivity (5 mol%, -80°C or rt, 24-72 h). Low enantioselectivies were induced ee 30-50%) depending on the amine used and the reaction temperature [79]. 

Complexes 92 and 93 also show good activity for the hydroamination of methacrylonitrile with morpholine, piperidine or A -methylpiperazine (70-93% conversion at 2.5 mol%, 90°C in 24 h) [80]. 

With some secondary amines, especially morpholine, the reaction leads to a mixture of the oxidative amination product and of the hydroamination product, both corresponding to an anh-Markovnikov addition (Eq. 4.39) [166]. 

Although the hydroamination of Michael systems is beyond the scope of this review, it is interesting to note the high yield (98%, TOE = 2 h ) obtained using the above cationic rhodium complexes for the hydroamination of 2-vinylpyridine with morpholine. Indeed, without catalyst, the hydroamination yield is only 5% [167]. 

The hydroamination of allene with morpholine or allylamines has been attempted with palladium-based catalysts. Usually, a mixture of 1 1 telomers (hydroamination products) and 1 2 telomers is obtained, the latter being the major [308, 309] or only... 

In the presence of oxygen the hydroamination products can not be obtained. Instead - especially with secondary amines or diamines - dehydrogenated di- and polyadducts are formed [79]. By reaction of morpholine or piperidine in air-saturated benzene solution the bisadduct, tetraadduct epoxide and the dimer shown in Figure 3.8 could be isolated and characterized. A defined 1,4-addition pattern is found in all these products. 

In addition, they carried out enantioselective Michael-type hydroamination of the alkenoyl-A-oxazolidinone 26 with aniline and obtained the chiral amine 27 with 93 % ee. Furthermore, they reported hydroamination of dihydrofuran (28) and 2,3-dihydropyran (30). Reaction of dihydrofioran (28) with morpholine proceeded at room temperature to give 2-aminotetrahydrofuran 29 regioselectively in high yield. Hydroamination of 2,3-dihydropyran (30) with morpholine proceeded at 80 "C to give 2-morpholinotetrahydropyran (31). For this hydroamination, phosphine-free... 

Interestingly, the Schafer group [34] has established that group 4 complexes can indeed be used for the intermolecular hydroamination of alkynes with secondary amines consistent with a shift in mechanism from the established [2+2] cycloaddition pathway. Specifically, a Zr ureate catalyst 5 has been developed to realize this shift in mechanism. For example, entry 20 shows that morpholine can be used at elevated temperatures to give enamine products that can be characterized in situ. Using the ureate catalyst 5, mechanistic analyses [35] and subsequent computational investigations [36] support a proton-assisted C-N bond formation (see later discussion). 

These results have been followed up with a Pt(ll) pincer complex that can realize the reaction of benzamide with 5.5 bar of ethylene at 100 °C for extended reaction times to achieve the desired N-ethyl-substituted amide [160]. Stoichiometric reactions with morpholine and the observed lack of catalytic turnover with this nucleophilic amine substrate point toward nucleophilic attack of coordinated ethylene as being the operative mechanism for this system [160]. Furthermore, by taking advantage of ongoing developments in Au-catalyzed hydroamination, Widenhoefer has shown that ethylene hydroureation can be realized with a gold(I) catalyst (22) with only 4 bar of ethylene pressure at 60 °C to give ethyl-substituted cycHc urea in outstanding yields (Scheme 15.22) [127]. 

Dzhemilev and Tolstikov et al. have studied the influence of phosphines and additives in the hydroamination of 1,3-butadiene with morpholine catalyzed by the Ni(acac)2/phosphine/AlEt3/ additive (1/3/3/10) system [180]. With CF3CO2H as additive, the reaction is highly selective (>93%) for the formation of l-(N-morpholino)-2-butene (>80% yield) by using P(w-Bu)3 or P(OEt)s as phosphine. With the same system and PCI3 as phosphine, a mixture of 3-(N-morpholino)-l-butene (70%) and l-(N-morpholino)-2-butene (30%) is formed (TOE = 21 h ). 

Ruthenium A hydroamination of styrenes ArC(Me)=CH2 with amines, such as piperidine or morpholine, can be catalysed by cationic Ru complexes in combination with chiral diphosphines, for example, [(C6H6)RuCl2]2 and xylylBINAP. The reaction has been reported to be -selective and the products ArC H(Me)CH2NR2 were obtained with <76% ee. ... 

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