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Allenylidene reactions with alcohols

A number of processes catalyzed by the dithiolate-bridged species have been mentioned already however, the extensive reactivity of alkynes within these systems has led to a number of more recent reports on their use in catalysis. The allenylidene complex 363 (R = Tol, R = Me 864 salt) has been identified as an intermediate in the catalysis of propargylic alcohol substitution reactions with alcohols in high yields and with complete regioselectivities... [Pg.688]

These reactions are thought to proceed by initial formation of the lithio propargylic alcohol adduct, which undergoes a reversible Brook rearrangement (Eq. 9.14). The resulting propargyllithium species can equilibrate with the allenyl isomer and subsequent reaction with the alkyl iodide electrophile takes place at the allenic site. An intramolecular version of this alkylation reaction leads to cyclic allenylidene products (Eq. 9.15). [Pg.506]

Unexpectedly, norbornene derivatives can undergo a novel cyclopropana-tion reaction with propargyl alcohol in the presence of cationic [(/f-Cp)(CH3CN)3Ru]+X catalysts, which have an electron-withdrawing substituent on the Cp ligand. Cyclopropanation products, exo-acetyltricyclooctanes, were obtained in good yields [50] (Eq. 37). The reaction has been shown not to involve the expected allenylidene intermediate but rather to lead to a ruthena-cycle intermediate and to a /i-hydroxy elimination. [Pg.17]

The activation of propargylic ethers also provides the generation of ruthenium allenylidene species with elimination of alcohols (Eq. 13). This reaction has been used in the catalytic transformation of benzyl propargyl ethers into 1,3-dienes via dealkoxylation, addition of benzyl alcohol to the a-carbon atom of the allenylidene intermediate and hydrogen-transfer reactions according to Scheme 21 [89]. [Pg.147]

In contrast to the C-H bonds of phenylacetylene, methane and acetone, the 0-H bonds of water and alcohols are added at the C -Cp double bond of the allenylidene ligand of 43 (Scheme 18) [20]. The reaction with water leads to the a,P-unsaturated hydroxycarbene [Ru(ri -C5H5) C(OH)CH=CPh2 (CO)(PTr3)]BF4... [Pg.206]

Figure 30. Isomeric, neutral, triruthenium allenylidene derivatives obtained from reactions with propargyl alcohols in basic methanolic solution. The terminal C-H has been omitted for clarity. Figure 30. Isomeric, neutral, triruthenium allenylidene derivatives obtained from reactions with propargyl alcohols in basic methanolic solution. The terminal C-H has been omitted for clarity.
The homobimetallic, ethylene-ruthenium complex 15, which contains three chloro bridges, was readily obtained from the reaction of [RuCl2(/ -cymene)]2 with 1 atm of ethylene [34]. In 2009, Demonceau and Delaude [34] showed that complex 15 could be a useful precursor to allow subsequent access to the diruthenium vinylidene complex 16, allenylidene complex 17, and indenylidene complex 18 (Scheme 14.8). Upon reaction with propargylic alcohol, complex 15 afforded vinylidene complex 16, which converted into the allenylidene complex 17 in the presence of molecular sieves [34]. As shown in the acid-promoted intramolecular rearrangement of mononuclear ruthenium allenylidene complexes [19, 20, 32], the addition of a stoichiometric amount of TsOH to complex 17 at -50 °C led to the indenylidene binuclear complex 18 [34]. Complex 18 has been well... [Pg.395]

Reactions with hetero-substituted alkynes are also examined. The dipropargylamine, MeN(GH2C=GH)2, reacts with Fe3(CO)i2 to provide a mixture of the bicyclic 4- and 5-type ferrole complexes, 9 and 10, as the major products," " while propargyl alcohols give allenylidene complexes, Fe3(GO)io(/x-C=C=CR2) (R2 = Me2, (GH2)s, Me/Ph) (see Section 6.08.2.3) via dehydration together with the 2- and 4-type complexes. " For a thiopropargyl system, see Chapter 6.07.7.2.2.1. [Pg.294]


See other pages where Allenylidene reactions with alcohols is mentioned: [Pg.201]    [Pg.66]    [Pg.238]    [Pg.253]    [Pg.87]    [Pg.4020]    [Pg.49]    [Pg.201]    [Pg.4019]    [Pg.226]    [Pg.248]    [Pg.379]    [Pg.93]    [Pg.575]    [Pg.591]    [Pg.687]    [Pg.267]    [Pg.231]    [Pg.34]    [Pg.346]    [Pg.667]    [Pg.668]    [Pg.140]    [Pg.153]    [Pg.155]    [Pg.159]    [Pg.161]    [Pg.163]    [Pg.179]    [Pg.179]    [Pg.197]    [Pg.197]    [Pg.200]    [Pg.203]    [Pg.234]    [Pg.17]    [Pg.64]    [Pg.65]    [Pg.67]    [Pg.68]    [Pg.72]   
See also in sourсe #XX -- [ Pg.219 ]




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