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Bridged adducts

The TMM [4-1-3] cycloaddition to pyrone has been employed in a synthetic study of a novel biologically active diterpene pseudolaric acid B (106), in which the formation of the bridged adduct (107) from the 2-pyrone (108) is the key step in the sequence (Scheme 2.29). A mixture of the other isomer (109) and the methylenecyclopentane (110) was also isolated from the reaction. It is important to point out that the presence of a tin co-catalyst is critical in effecting the reaction. This is the first example a "tin-effect observed in a [4-1-3] cycloaddition [40]. [Pg.77]

Type 1. Bridging adducts (see Fig. 2), where the dioxygen ligand is bridged between two metal atoms intermolecularly. Here, the metal dioxygen ratio is invariably 2 1. [Pg.5]

Like sulfur, selenium based electron donors are heavily studied due to their potential as antithyroid agents. Of the 28 complexes reported, the majority (20) are diiodine based, and most of these (16) are simple adducts. One diiodine complex is bridged, one contains only extended adducts, one contains only bridged adducts, and one contains both bridged and extended adducts. All of the interhalogen complexes are simple adducts except one with iodine monobromine, which forms an extended adduct. [Pg.99]

A mixture prepared at 0°C with a 3 1 molar excess of halocarbon exploded violently soon after removal of the ice bath. Formation of a 1 1 chlorine-bridged adduct was assumed. [Pg.833]

Acylnitroso compounds 197 (R = Me, Ph or Bn) react in situ with 1-methoxycarbonyl-1,2-dihydropyridine to yield solely the bridged adducts 198 quantitatively. On the other hand, 1 1 mixtures of the regioisomers 199 and 200 were formed from the nitroso-formates 187 (R = Me or Bn) (equation 110)103. The chiral acylnitroso compounds 201 and 202, which are of opposite helicity, add to cyclohexadiene to give optically active dihydrooxazines in greater than 98% diastereomeric excess (equations 111 and 112)104. Similarly, periodate oxidation of the optically active hydroxamic acid 203 in the presence of cyclopentadiene, cyclohexa-1,3-diene and cyclohepta-1,3-diene affords chiral products 204 (n = 1, 2 and 3, respectively) in 70-88% yields and 87-98% de (equation 113)105. [Pg.520]

This means that either /r 2 or k is 0.21 M order redox process which (1.117) represents, but is very unlikely for k 2 since formation of the bridged adduct must involve Co "-0 bond cleavage in Co(edta) and such a process would be expected to be much slower (Ch. 4). For this, and other reasons mechanism (b) is strongly preferred. [Pg.26]

Fulleroids Bridged Adducts with Open Transannular Bonds... [Pg.345]

Scheme 11.1 Ring opening reaction from a hypothetical [5,6 -bridged adduct to a fulleroid. Scheme 11.1 Ring opening reaction from a hypothetical [5,6 -bridged adduct to a fulleroid.
The rare reports of quinolizidine formation by a nitrone cycloaddition strategy include the racemic total synthesis of lasubine II (58), one of a series of related alkaloid isolated from the leaves of Lagerstoemia subcostata Koehne (Scheme 1.14) (104). While these alkaloids were previously accessed by infennolecular nitrone cycloaddition reactions, this more recent report uses an intramolecular approach to form the desired piperidine ring. Thus, cycloaddition of nitrone 59 affords predominantly the desired bridged adduct 60 along with two related... [Pg.13]

Methylmethine-bridged adducts Epicatechin-CH-CHj-malvidin 3-glc (two isomers)... [Pg.281]

Some examples of three-membered chelate rings containing N and S are known. iV-Sulfinyl-aniline, and substituted forms, has been shown to bond in this manner to give chelates of the type (43) with a number of metal ions in low oxidation states. Such compounds have been reported with Ni0,150 with Rh1 and Ir1,151 and with Fe0.152 A similar bonding mode has been demonstrated for 4-(methyl)thionitrosobenzene in a bridged adduct of general form [Fe2(CO)6L].153... [Pg.804]

Formation of para-bridge-adducts of type 106 will be discussed in Section III.D.l according to mechanism of the coordinated cycloaddition or para-cyclization (84UK1648). [Pg.183]

Diels-Alder reactions involving cyclic dienes give rise to bridged adducts. Any substituent X found at the bridge may adopt a syn or anti position with respect to the double bond ... [Pg.158]


See other pages where Bridged adducts is mentioned: [Pg.23]    [Pg.166]    [Pg.259]    [Pg.5]    [Pg.18]    [Pg.22]    [Pg.75]    [Pg.1074]    [Pg.85]    [Pg.247]    [Pg.46]    [Pg.48]    [Pg.302]    [Pg.134]    [Pg.298]    [Pg.343]    [Pg.202]    [Pg.123]    [Pg.37]    [Pg.39]    [Pg.43]    [Pg.43]    [Pg.277]    [Pg.288]    [Pg.537]    [Pg.823]    [Pg.47]    [Pg.53]    [Pg.53]    [Pg.201]    [Pg.212]    [Pg.168]    [Pg.181]   


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Bridging ligands nickel adducts

Fulleroids Bridged Adducts with Open Transannular Bonds

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