Imines carbonyl-alkene couplings

Catalytic Reductive Coupling of Alkenes and Alkynes to Carbonyl Compounds and Imines Mediated by Hydrogen... 

Ihmels H, Otto D (2005) Intercalation of Organic Dye Molecules into Double-Stranded DNA - General Principles and Recent Developments. 258 161-204 Iida H, Krische MJ (2007) Catalytic Reductive Coupling of Alkenes and Alkynes to Carbonyl Compounds and Imines Mediated by Hydrogen. 279 77-104 Imai H (2007) Self-Organized Formation of Hierarchical Structures. 270 43-72 Indelli MT, see Chiorboli C (2005) 257 63-102 Inoue Y, see Borovkov VV (2006) 265 89-146 Ishii A, Nakayama J (2005) Carbodithioic Acid Esters. 251 181-225 Ishii A, Nakayama J (2005) Carboselenothioic and Carbodiselenoic Acid Derivatives and Related Compounds. 251 227-246... 

The Ti-promoted coupling between an alkene or alkyne and another 7t-bonded compound, such as an alkene, a carbonyl compound, or an imine, may be classified as follows ... 

Kobayashi et al. found that lanthanide triflates were excellent catalysts for activation of C-N double bonds —activation by other Lewis acids required more than stoichiometric amounts of the acids. Examples were aza Diels-Alder reactions, the Man-nich-type reaction of A-(a-aminoalkyl)benzotriazoles with silyl enol ethers, the 1,3-dipolar cycloaddition of nitrones to alkenes, the 1,2-cycloaddition of diazoesters to imines, and the nucleophilic addition reactions to imines [24], These reactions are efficiently catalyzed by Yb(OTf)3. The arylimines reacted with Danishefsky s diene to give the dihydropyridones (Eq. 14) [25,26], The arylimines acted as the azadienes when reacted with cyclopentadiene, vinyl ethers or vinyl thioethers, providing the tet-rahydroquinolines (Eq. 15). Silyl enol ethers derived from esters, ketones, and thio-esters reacted with N-(a-aminoalkyl)benzotriazoles to give the /5-amino carbonyl compounds (Eq. 16) [27]. The diastereoselectivity was independent of the geometry of the silyl enol ethers, and favored the anti products. Nitrones, prepared in situ from aldehydes and N-substituted hydroxylamines, added to alkenes to afford isoxazoli-dines (Eq. 17) [28]. Addition of diazoesters to imines afforded CK-aziridines as the major products (Eq. 18) [29]. In all the reactions the imines could be generated in situ and the three-component coupling reactions proceeded smoothly in one pot. 

The spectrum of applications of potassium permanganate is very broad. This reagent is used for dehydrogenative coupling [570], hydrox-ylates tertiary carbons to form hydroxy compounds [550,831], hydroxylates double bonds to form vicinal diols [707, 296, 555, 577], oxidizes alkenes to a-diketones [560, 567], cleaves double bonds to form carbonyl compounds [840, 842, 552] or carboxylic acids [765, 841, 843, 845, 852, 869, 872, 873, 874], and converts acetylenes into dicarbonyl compounds [848, 856, 864] or carboxylic acids [843, 864], Aromatic rings are degraded to carboxylic acids [575, 576], and side chains in aromatic compounds are oxidized to ketones [566, 577] or carboxylic acids [503, 878, 879, 880, 881, 882, 555]. Primary alcohols [884] and aldehydes [749, 868, 555] are converted into carboxylic acids, secondary alcohols into ketones [749, 839, 844, 863, 865, 886, 887], ketones into keto acids [555, 559, 590] or acids [559, 597], ethers into esters [555], and amines into amides [854, 555] or imines [557], Aromatic amines are oxidized to nitro compounds [755, 559, 592], aliphatic nitro compounds to ketones [562, 567], sulfides to sulfones [846], selenides to selenones [525], and iodo compounds to iodoso compounds [595]. 

Alkenes. The low-valent titanium species is useful for defunctionalization of l-(2-hydroxyalkyl)benzotriazoles. The reagent is activated by the addition of stoichiometric amounts of iodine for the McMuny coupling of carbonyl compoimds. 1,2-Diamines Reductive dimerization of imines affords diamines which are valuable ligands. 

The [i-aUyl complexes can react with several types of nucleophiles, giving rise to the corresponding substitution products. O- and N-nucleophiles as well as soft carbon nucleophiles attack the t-allyl complex directly at the aUylic position, while hard C-nucleophiles react via transmetaUations [2c, 3]. If the nucleophihc attack occurs under an atmosphere of CO, insertion of CO can occur, yielding carbonyl compounds [4]. Alkenes and aUcynes can also insert into allyhnetal bonds, a protocol that is used preferentially for cycUzations [5]. Cyclizations can also occur, if the 7t-allylmetal complex contains an internal nucleophilic center. If the metalallyl complex acts as a nucleophile, direct coupling with aryl halides [6] or additions to electrophiles such as aldehydes, ketones, or imines are possible [7]. This review focuses on C-C coupling reactions via these tt-allyhnetal (or in some cases, a-allyhnetal) intermediates. 

Overall, the carbonylation of alkynes is rather complex, but it is possible to draw a general trend and to divide these processes into three classes depending on the alkyne (i) For most internal alkynes, the carbon-carbon bond-forming process can involve an acylpalladation step whether there is an isomerization or not. (ii) However, some of them may involve an electrophilic activation of the triple bond by the acylpalladium complex followed by nucleophilic attack and reductive elimination, (iii) On the other hand, terminal alkynes appear to undergo mostly cross-coupling for the first carbon-carbon bond formation. Aside from these mechanistic intricacies, it is important to point out that these processes usually involve incorporation of more than one molecule of CO and creation of two to three carbon-carbon bonds in one reaction, and they yield heterocycles in fair to good yields. Other multiple bond systems like alkenes, imines or dienes also provide nice entries to carbo- and heterocycles. The limitations are usually due to the necessary time balance between acylpalladation and the termination step to avoid polymeric or decarbonylation processes. 

Carbon-heteroatom double bonds can also participate in this reaction. These include both carbonyl compounds (Scheme 11.37) and imines (Scheme 11.38). Addition to aldehydes is co-catalysed by tin(II) or indium(III) salts. Under these conditions, tetrahydrofiirans are obtained. The presence or absence of the co-catalyst can also switch the reaction from one mode to another (Scheme 11.39). An indium cocatalysed cycloaddition to a 7-pyrone aldehyde 11.117 was used in a synthesis of aureothin 11.122 and A-acetylaureothamine 11.123 (Scheme 11.40). Cross-metathesis of the exo-cyc ic alkene 11.118 allowed a subsequent Suzuki coupling with a gem-dibromide 11.120 that showed the expected selectivity (Section 2.1.4.2). This reaction required the use of thallium ethoxide as the Lewis base to suppress the formation of side products. A Negishi coupling completed the synthesis of aureothin 11.122. Reduction and acylation of the nitro group yielded A-acetylaureothamine 11.123. The latter compound is active digainst Helicobacter pylori, a bacterium behind stomach ulcers. 

Aldehydes and ketones are useM building blocks in organic synthesis. The direct a-C-H substitutions of carbonyl compounds are well known. However, selective P-C(sp )-H functionalization remains rare. The MacMillan group introduced Site activation model by dual aminocatalysis and photocatalysis, opening up a practical synthetic route to P-substituted aldehydes and ketones (Scheme 3.25). With this novel strategy, radical-radical coupling of enaminyl radical with electron-poor cyanobenzene radical anion can elegantly produce P-aiylated aldehydes and ketones [74]. A recombination of enaminyl radical with imine anion radical was also developed [75]. In the presence of Michael acceptors, radical addition of enaminyl radical to electron-deficient alkenes affords P-alkylated aldehydes [76]. 

Generally, the alkynes can be prepared by the following two types of methods (3-elimination of CF3-containing hal-ogenated alkenes and a cross-coupling of trifluoromethy-lated acetylide with various halides in the presence of palladium catalyst, as shown in Scheme 26.49. Additionally, the reaction of the lithium acetylide with various electrophiles, such as carbonyl compounds, imines, and... 

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