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Cyclisation-addition reaction

Scheme 7.34 Domino cyclisation-addition reaction catalysed by chiral phosphoric acid catalysis and gold catalysis. Scheme 7.34 Domino cyclisation-addition reaction catalysed by chiral phosphoric acid catalysis and gold catalysis.
Standard cyclisation methodology was used to access the cyclic monophosphinic acid derivative 78 by reaction of ammonium phosphonate and ethyldiisopropylamine, followed by the addition of chlorotrimethylsilane, with 2,2 -bis (bromomethyl)-l,l -biphenyl. Silane reduction of 78 gave the secondary phosphine. The secondary phosphine borane complex 79 could be used in alkylation or Michael addition reactions. For example the Michael adduct 80 was produced in high yield by treatment of 78 with a NaH suspension in THF followed by the addition of diethylvinylphosphonate . [Pg.356]

Polar Cycloadditions R. R. Schmidt, Angew. Chem., Int. Ed. Engl., 1973, 12, 212-224. Addition Reactions with Intramolecular Cyclisation V. I. Staninets and E. A. Shilov, Russ. Chem. Rev. (Engl. Transl.), 1971, 40, 272-283. [Pg.55]

The intramolecular carbon-carbon bond-forming reactions considered in this section are based on the aldol condensation (see Section 5.18.2, p. 799), the Claisen-Schmidt reaction (see Section 6.12.2, p. 1032), the Claisen ester condensation (see Section 5.14.3, p. 736), and the Claisen reaction (see Section 6.12.2, p. 1032). Since these carbonyl addition reactions are reversible, the methods of synthesis are most successful for the formation of the thermodynamically stable five- and six-membered ring systems. The preparation of the starting materials for some of these cyclisation reactions further illustrates the utility of the Michael reaction (see Section, 5.11.6, p. 681). [Pg.1092]

Termination steps can be caused by radical-radical combinations which remove radicals from the chain reaction. An example of a chain reaction using the commonly encountered tributyltin hydride (BusSnH) to carry out a radical cyclisation is shown in Scheme 10.3 to illustrate SH2 and addition reactions. The radicals act as the chain carriers, each reacting with a neutral molecule, and when a radical is removed from the chain by termination, the chain breaks down. [Pg.264]

Conclusion As expected, the double cyclisation of bicyclo-phosphanes induces a strong ring constraint. The marked tendency of these compounds to oligomerization by rupture of the P-0 bond is certainly favoured because it minimizes this tension. The driving force of the addition reaction of X-H molecules is the great stability of the bicyjJjphosphorane structure. Depending upon the nature of X, the P tautomer forms of the last compounds could be observed or not. [Pg.278]

The addition of organolithiums to polarised C=X bonds is one of the most widely used ways of making C-C bonds, and (excepting some unusual intramolecular cases) will not be discussed in this book other than to say it is a reliable and successful reaction. With a few exceptions,1 3 stereoselectivity is not a general feature of organolithium addition reactions to C=0 n bonds. Much of this chapter will concern controlled addition of organolithiums to C=C 7i bonds after an overview of carbolithiation, we shall review the development of intramolecular carbolithiation, or anionic cyclisation. [Pg.273]

Benzophenones have been described as useful sensitisers for PET catalysed conjugate addition reactions of a-amino alkyl radicals to enones (Bertrand et al. 2000). We tried to modify this reaction and synthesised the pyrrolidinylethyl-substituted quinolone 35 from the known bromide (Bauer et al. 2005). Upon electron transfer from the pyrrolidine to a given acceptor, a radical cyclisation occurs (Scheme 15), which after electron and proton transfer generates a pyrrolizidine. We found 4,4/-dimethoxybenzophenone to be a suitable catalyst for this reaction. Remarkably, the reaction proceeded with excellent simple diastereos-electivity and a single diastereoisomeric product rac-36 was obtained. With 10 mol% of the catalyst, a chemical yield of 71% was achieved. [Pg.273]

Scheme 7.10 Indium-mediated tandem radical addition-cyclisation-trapping reactions in aqueous media. Scheme 7.10 Indium-mediated tandem radical addition-cyclisation-trapping reactions in aqueous media.
Irradiation of the thiopyran derivative (292a) results in extrusion of HNCS and the formation of the pyridine (292b, 63.3%) as the major product. The photochemical reactivity of the pyranthione (293) is concentration dependent in 3-methylpentane as solvent. At low concentrations the thione reacts with the solvent but at higher concentrations the main reaction is the production of thiyl radicals. Laser flash photolysis has been used to identify that the triplet excited state of (294) is involved in addition reactions which occur to electron deficient alkenes such as acrylonitrile giving (295), for example. Other compounds related to thiourea are also photochemically reactive. Thus the photochemical cyclisation of (296) to afford (297) has been reported. ... [Pg.276]

Unsaturated polymers undergo reactions such as isomerisation, cyclisation, addition, epoxidation and hydrogenation. Saturated polymeric hydrocarbons undergo substitution on the main chain or the side chain. Loaded butyl vulcanisates were shown to be less... [Pg.94]

According to the original process of Addor (1962), phospholan is prepared by the reaction of ethylene-1,2-dithiol with cyanogen chloride, followed by the reaction of 2-imino-l,3-dithiolane (103) with diethyl phosphorochloridate. According to his later process (1970), N-(0,0-diethylphosphoryl) dithiocarbamate (104), obtained by the addition reaction of diethyl phosphoryl isothiocyanate and potassium hydrosulilde, is cyclised with ethylene bromide. [Pg.151]

The adduct (112) from phenyldichlorophosphine and stilbene undergoes a highly stereo selective oxidative addition reaction with o-aminophenol to form the cis-spirophosphorane (113) whose structure was confirmed (as the benzyl derivative) by X-ray crystallography and found to possess almost perfect tbp geometry. On the other hand, the reaction of (112) with catechol led stereoselectively to the trans configuration of the spirophosphorane (114)35. Cyclisation of (115) with PhPCl2 yields (116) which undergoes oxidative cycloaddition with 2,3-butanedione (117) to form the cis and trans forms of the - diphosphaspiro [4,4] -nonane (118).36... [Pg.67]

The use of acyclic precursors by Claisen cyclisation or Diels-Alder addition reactions. [Pg.140]

Gunstone, F.D., and R.G. Powell, An Addition Reaction of Methyl Linoleate Accompanied by Cyclisation, Chem. Phys. Lipids 2 203-212 (1968). [Pg.17]

In 2010, Jorgensen et al. developed an enantioselective tandem reaction of propargylated malononitriles with cyclic enones sequentially catalysed by a cinchona alkaloid-derived primary amine catalyst in the presence of (J )-mandelic acid as an additive for the first Michael step, and a gold catalyst for the second tandem exo-dig cyclisation-isomerisation reaction. " As shown in Scheme 7.62, the corresponding chiral bicyclic enones were achieved in good yields and high enantioselectivities of up to 96% ee, albeit low to moderate diastereoselectivities (34-66% de). [Pg.168]

Stabilised sulphur ylides react with alkenylcarbene complexes to form a mixture of different products depending on the reaction conditions. However, at -40 °C the reaction results in the formation of almost equimolecular amounts of vinyl ethers and diastereomeric cyclopropane derivatives. These cyclopropane products are derived from a formal [2C+1S] cycloaddition reaction and the mechanism that explains its formation implies an initial 1,4-addition to form a zwitterionic intermediate followed by cyclisation. Oxidation of the formed complex renders the final products [30] (Scheme 8). [Pg.68]


See other pages where Cyclisation-addition reaction is mentioned: [Pg.452]    [Pg.43]    [Pg.171]    [Pg.114]    [Pg.88]    [Pg.415]    [Pg.31]    [Pg.452]    [Pg.13]    [Pg.302]    [Pg.77]    [Pg.80]    [Pg.43]    [Pg.745]    [Pg.771]    [Pg.171]    [Pg.171]    [Pg.188]    [Pg.255]    [Pg.50]    [Pg.142]    [Pg.313]    [Pg.140]    [Pg.70]    [Pg.302]    [Pg.68]    [Pg.70]   
See also in sourсe #XX -- [ Pg.124 ]




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Cyclisation reactions

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