Alkenes diamination reactions

Three different approaches to the synthesis of five-membered cyclic ureas have recently been described that involve Pd-catalyzed alkene diamination reactions. In a series of very interesting papers, Muniz has described the conversion of alkenes bearing pendant ureas to imidizolidin-2-one derivatives using catalytic amounts of Pd(OAc)2 in the presence of an oxidant such as PhI(OAc)2 or CuBr2 [61, 62]. For example, these conditions were used to effect the cyclization of 79 to 80 in 78% yield (Eq. (1.34)) [62aj. These reactions proceed via a mechanism similar to that shown above in Eq. (1.33), except that the heteropalladation may occur in a syn- rather than anti- fashion, and the reductive elimination occurs with intramolecular formation of a C—N bond rather than intermolecular formation of a C—O bond. The alkene diamination reactions have also been employed for the synthesis of bisindolines (Eq. (1.35)) [63] and bicyclic guanidines (Eq. (1-36)) [64]. 

The scope of this chemistry has recently been extended to terminal alkene substrates [68]. For example, 1-hexene was transformed to 88 in 68% yield under solvent-free conditions using Pd(PPh3)4 as catalyst (Eq. (1.39)). Asymmetric induction has also been achieved in these reactions, and ees of up to 94% have been obtained with a catalyst supported by a chiral phosphoramidite ligand [68c]. The mechanism of the terminal alkene diamination reactions has not yet been fiiDy elucidated, but it appears likely that allyUc C H activation/amination is involved. 

Reactions of Pt(O,0-MeCOCHCOMe)(MeCOCH2COMe)X (X = Cl, Br) with a wide variety of donors, including phosphines, arsines, amines, alkenes, diamines, etc. have been examined. In all cases the coordinated neutral acetylacetone is displaced. When monodentate ligands, L, are employed, products are of the type Pt(0,0-MeCOCHCOMe)XL. Bidentate ligands, LL, yield Pt(C-MeCOCHCOMe)X(LL) and bridging alkenes form PtCl(0,0-MeCOCHCOMe) (dialkene).494... 

Recently the diamination reaction of alkenes attracted much attention (reviews [377, 378]). Shi and coworkers disclosed a versatile palladium-catalyzed intermo-lecular diamination methodology [379]. For dienes, this process is selective for the internal double bond and occurs according to a classical two-electron catalytic... 

Diamination of alkenes. This reaction can be effected with a primary or secondary aromatic amine (2 equiv.) and 1 equiv. of 1 in refluxing THF (4 hours). 

An additional reaction with transfer of nitrogen and oxygen to alkenes was also observed as a side reaction in certain diamination reactions with ureas. It is discussed within the following section. 

The combination of palladium(II) catalysts with stoichiometric amounts of cop-per(I I) salts as oxidants allowed the subsequent development of further diamination reactions. A particularly attractive approach to cychc guanidines 144 from easily accessible precursors 143 was realized within such a diamination reaction of alkenes (Scheme 16.38) [SK)]. It is interesting to note that the reaction proceeds already with copper(II) dichloride and with unprecedentedly enhanced rates also for piperidine formation. The selection of carbamate protecting groups readily provides the free guanidinium products within a single-step transformation. 

In recent years, a number of novel palladium-catalyzed diaslereoselective alkene difunctionalization reactions, such as aminohalogenation [34], aminoacetoxylation [35], aminofluorination [36], and diamination [37], have been studied intensively by the combination of other reactions with an amino- or oxopaUadation reaction. In some of these transformations, a Pd(IV) species is believed to be the key intermediate (Scheme 6.21). 

Episulfides, which can be generated in situ in various ways, react similarly to give P-amino thiols, and aziridines give 1,2-diamines. Triphenylphosphine similarly reacts with epoxides to give an intermediate that undergoes elimination to give alkenes (see the Wittig reaction, 16-47). 

Primary (R = H) and secondary aromatic amines react with alkenes in the presence of thallium(III) acetate to give vie- diamines in good yields. " The reaction is not successful for primary aliphatic amines. In another procedure, alkenes can be diaminated by treatment with the osmium compounds R2NOSO2 and R3NOSO (R = t-Bu)," analogous to the osmium compound mentioned at 15-51. The palladium-promoted method of 15-51 has also been extended to diamination. " Alkenes can also be diaminated indirectly by treatment of the aminomercurial compound mentioned in 15-51 with a primary or secondary aromatic amine. 

The [(T -C3H5)PdCl]2/dppf/AcOH catalytic system has been used for the bis(hy-droamination) of 3-alken-l-ynes to alkenic 1,4-diamines (Eq. 4.94), a reaction which seems to be mechanistically related to the hydroamination of allenes since an a-al-lenic amine CH2=C=CH(R )CH2NR2 is believed to be an intermediate [318]. 

The reactions of olefins with non-organometallic Tc(VII) compounds behaved similarly. In a recent study, [Tc03C1(AaA)] (86a) (in which AA stands for aromatic diamine derivatives) was shown to react quantitatively with olefins, and produce the corresponding Tc(V) diolato-complex [TcOC1(OaO)(AaA)] (87a). The process could not be run catalytically, as Tc(V) complexes tend to undergo disproportionation rather than reoxidation in the presence of water [97]. These alkene-glycol interconversions could not be performed with the analog Re(VII) compound. Rhenium displays completely contrary behaviour, in that alkenes can... 

A Cu(OAc)2-catalyzed intramolecular diamination of alkenes using sulfamide substrates such as compound 214 provides a route to fused thiadiazolidines 215 (Equation 48) <2005JA11250>. In this reaction, the transition metal activates the alkene toward nucleophilic attack by the first nitrogen, then becomes displaced by the second nitrogen nucleophile (a net M +z to M reduction). 

Brunner, Leitner and others have reported the enantioselective transfer hydrogenation of alpha-, beta-unsaturated alkenes of the acrylate type [50]. The catalysts are usually rhodium phosphine-based and the reductant is formic acid or salts. The rates of reduction of alkenes using rhodium and iridium diamine complexes is modest [87]. An example of this reaction is shown in Figure 35.8. Williams has shown the transfer hydrogenation of alkenes such as indene and styrene using IPA [88]. 

Since Sharpless discovery of asymmetric dihydroxylation reactions of al-kenes mediated by osmium tetroxide-cinchona alkaloid complexes, continuous efforts have been made to improve the reaction. It has been accepted that the tighter binding of the ligand with osmium tetroxide will result in better stability for the complex and improved ee in the products, and a number of chiral auxiliaries have been examined in this effort. Table 4 11 (below) lists the chiral auxiliaries thus far used in asymmetric dihydroxylation of alkenes. In most cases, diamine auxiliaries provide moderate to good results (up to 90% ee). 

In summary, the reaction of osmium tetroxide with alkenes is a reliable and selective transformation. Chiral diamines and cinchona alkakoid are most frequently used as chiral auxiliaries. Complexes derived from osmium tetroxide with diamines do not undergo catalytic turnover, whereas dihydroquinidine and dihydroquinine derivatives have been found to be very effective catalysts for the oxidation of a variety of alkenes. OsC>4 can be used catalytically in the presence of a secondary oxygen donor (e.g., H202, TBHP, A -methylmorpholine-/V-oxide, sodium periodate, 02, sodium hypochlorite, potassium ferricyanide). Furthermore, a remarkable rate enhancement occurs with the addition of a nucleophilic ligand such as pyridine or a tertiary amine. Table 4-11 lists the preferred chiral ligands for the dihydroxylation of a variety of olefins.61 Table 4-12 lists the recommended ligands for each class of olefins. 

In a similar manner, polymers with unsaturated chains or side chains can be converted to polyamines [66-69]. Conjugated diolefins usually undergo hydroformylation with low selectivities [70]. Mostly hydrogenation of at least one double bond occurs and mixtures of various saturated and unsaturated amines and diamines are obtained [71]. Similar to alkenes also alkynes may serve as unsaturated compounds in hydro aminomethylation reaction sequences. Although synthetically attractive, only a few investigations towards hydroformylation and hydroaminomethylation of alkynes in the presence of N-nuclcophilcs are known. Usually a preferred transformation to furanonic derivatives is observed under hydroformylation conditions [27]. 

The dimerization of functional alkenes such as acrylates and acrylonitrile represents an attractive route to obtain bifunctional compounds such as dicarboxylates and diamine, respectively. The head-to-tail dimerizahon of acrylates and vinyl ketones was catalyzed by an iridium hydride complex generated in situ from [IrCl(cod)]2 and alcohols in the presence of P(OMe)3 and Na2C03 [26]. The reaction of butyl acrylate 51 in the presence of [IrCl(cod)]2 in 1-butanol led to a head-to-tail dimer, 2-methyl-2-pentenedioic acid dibutyl ester (53%), along with butyl propionate (35%) which is formed by hydrogen transfer from 1-butanol. In order to avoid... 

O Grady et al. (12), used a high-surface sodium on alumina catalyst at 25° for the isomerization of 4-methylcyclohexene and observed the formation of the three methylcyclohexene isomers (C). 4-Methylcyclohexene has also been isomerized by Reggel et al. (4), using the lithium ethylene diamine system. In general the reaction of cyclenes and the mechanism thereof may be considered to be like that of alkenes. 

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