Adducts in complexes

Ma, L., Zhang, H., Humphreys, G., Sanders, M., and Zhu, M. (2005). Selective and sensitive detection of GSH adducts in complex biological samples using high resolution LC/FIMS with mass defect filtering. In Proceedings of the 53rd ASMS Conference on Mass Spectrometry and Allied Topics, San Antonio, TX. 

A quinoline—bromine adduct in hot carbon tetrachloride containing pyridine gives a 90% yield of 3-bromoquinoline (21) 3-chloroquinoline [612-59-9] is prepared by an analogous route, but in poorer yield. A quinoline—aluminum chloride complex heated with bromine gives a 78% yield of 5-bromoquinoline [165-18-3] (22). Equal quantities of 5- and 8-bromoquinoline [16567-18-3] are formed when quinoline is treated with one equivalent of bromine in concentrated sulfuric acid containing silver sulfate (23). 

Sulfur trioxide reactivity can also be moderated through the use of SO adducts. The reactivity of such complexes is inversely proportional to their stabihty, and consequentiy they can be selected for a wide variety of conditions. Whereas moderating SO reactivity by adducting agents is generally beneficial, the agents add cost and may contribute to odor and possible toxicity problems in derived products. CeUulosic material has been sulfated with SO.—trimethyl amine adduct in aqueous media at 0 to 5°C (16). Sulfur trioxide—triethyl phosphate has been used to sulfonate alkenes to the corresponding alkene sulfonate (17). Sulfur trioxide—pyridine adduct sulfates oleyl alcohol with no attack of the double bond (18). 

This binuclear complex is also fluxional and has the structure shown in Fig. 7.4a. A1(BH4)3 reacts readily with NMe3 to give a 1 1 adduct in which Al adopts the unusual pentagonal... 

Evans et al. reported that the his(oxazolinyl)pyridine (pybox) complex of copper(II) 17 is a selective catalyst of Diels-Alder reactions between a-bromoacrolein or methacrolein and cydopentadiene affording the adducts in high enantioselectivity [23] (Scheme 1.30). Selection of the counter-ion is important to achieve a satisfactory reaction rate and enantioselectivity, and [Cu(pyhox)](ShFg)2 gave the best result. This catalyst is also effective for the Diels-Alder reaction of acrylate dieno-philes (vide infra). 

Evans s bis(oxazolinyl)pyridine (pybox) complex 17, which is effective for the Diels-Alder reaction of a-bromoacrolein and methacrolein (Section 2.1), is also a suitable catalyst for the Diels-Alder reaction of acrylate dienophiles [23] (Scheme 1.33). In the presence of 5 mol% of the Cu((l )-pybox)(SbF5)2 catalyst with a benzyl substituent, tert-butyl acrylate reacts with cyclopentadiene to give the adduct in good optical purity (92% ee). Methyl acrylate and phenyl acrylate underwent cycloadditions with lower selectivities. 

Trialkylaluminum and diethyl ether - triorganoaluminum complexes undergo addition to l-ni-trocycloalkenes in hexane at 0°C or 60°C, respectively to give adducts in good yield23. 

Other examples that involve intermediate allyl cations are illustrated in Scheme 1.4. The cationic palladium(II) complex [Pd(dppp)(PhCN)2](BF4)2 coordinates the carbonyl oxygen of benzaldehyde and the activated carbonyl carbon attacks the isoprene, forming the allyl cation 10 which then cyclizes to give the 4-methyl-6-phenyl-5,6-dihydro-2H-pyran [22]. 2-Oxopropyl acrylate 11, in the presence of trimethylsilyltrifluoromethane sulfonate (TMSOTf) and methoxytrimethylsilane (MeOSMT), generates the cation 11a which is an efficient dienophile that reacts easily with the cyclohexadiene to give the Diels-Alder adduct in good yield [23]. 

Nafion-H (144), a perfluorinated resin-sulfonic acid, is an efficient Bronsted-acid catalyst which has two advantages it requires only catalytic amounts since it forms reversible complexes, and it avoids the destruction and separation of the catalyst upon completion of the reaction [94], Thus in the presence of Nafion-H, 1,4-benzoquinone and isoprene give the Diels-Alder adduct in 80% yield at 25 °C, and 1,3-cyclohexadiene reacts with acrolein at 25 °C affording 88 % of cycloadduct after 40 h, while the uncatalyzed reactions give very low yields after boiling for 1 h or at 100 °C for 3.5 h respectively [95], Other examples are given in Table 4.24. In the acid-catalyzed reactions that use highly reactive dienes such as isoprene and 2,3-dimethylbutadiene, polymerization of alkenes usually occurs with Nafion-H, no polymerization was observed. 

Addition of anhydrous LiX (X = OH, Cl, Br, 1) to Li[Bu"C(NBu%] in THF afforded laddered aggregates in which two neutral lithium amidinates chelate one LiX unit. When the added salt is Lil, the monomeric laddered aggregate is isolated as a bis-THF adduct. In the case of LiOH, LiCl, and LiBr, the ladders dimerize about their external LiX edges. This process is highlighted in Scheme 10 for LiOH. The molecular structure of the resulting dimeric ladder complex is depicted in Figure 2. °... 

The heavy alkaline earth metals Ca, Sr, and Ba react with 2 equivalents of NJ -bis(2,6-diisopropylphenyl)formamidine in the presence of bis(pentafluorophenyl)-mercury to afford the bis(formamidinato) species as THF adducts in good to moderate yield (Scheme 23). When the same reactions are carried out in a 1 1 molar ratio, N-p-tetrafluorophenyl-N,N -bis(2,6-diisopropylphenyl)formamidine is isolated as the sole product in all cases (Scheme 23). Other substituted N -bis(aryl)formamidinate complexes of the heavy alkaline earth metals were synthesized accordingly. ... 

Fujisawa et al. [Ill] have reported that the magnesiiun complex prepared from chiral 2-[2-[(tolylsulfonyl)amino]phenyl]-4-phenyl-l,3-oxazoline 81 and methyl-magnesium iodide was efficient, in a stoechiometric amount, for promoting the enantioselective Diels-Alder reaction of 3-alkenoyl-l,3-oxazohdin-2-one with cyclopentadiene (Scheme 45) leading exclusively to the endo adducts in up to 92% ee. The use of 10 mol% of the complex led to an important decrease in enantioselectivity of the product (51% ee). 

This supramolecular approach has been used as a way to facilitate the crystallization of cuboidal aqua ions and to capture single intermediates present in complex solution mixtures. For example, [M3Q4Clx(H20)9.x] (Q = S, Se) supramolecular adducts have been isolated for x =1-5 from aqueous HCl solutions by varying the acid concentrations where the aggregates contain in each case only one of all possible isomers [46]. In addition to the hydrogen bonds, other kinds of interactions, namely C1---H20, C1---C1 and Q---Q contacts, are also involved in the network propagation. This supramolecular approach has also been efficiently employed for the crystallization of a large number of aqua complexes within the [M3M Q4] cubane-type family, where M is a transition or post-transition metal [47]. 

CO species in the adducted triiron complexes, the propargylidene-ketene compoimd has e same structure as compound 5 (ii) desilylation by the substitution of the silyl termin species with the ion originating from H2O or the solvent gives the hydrogen-ketene form. 

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