- Heptafulvenone, vinylketene, butadienylketene, and allenylketene - Facile generation, observation, and radical reaction with TEMPO
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Heptafulvenone (1), vinylketene (11), 1,3-butadienylketene [(E)-15], and allenylketene (21) have been prepared by reaction of the corresponding acyl chlorides with 1,8-bis(dimethylamino)naphthalene as long-lived species in solution at room temperature, and their ketenyl IR bands observed under these conditions for the first time, at 2101, 2118, 2111, 2117 cm-1, respectively. These unsaturated ketenes react with tetramethylpiperidinyloxyl (TEMPO, TO.) with initial attack at the carbonyl carbon giving delocalized radicals which give from 1 a mixture of the ring contracted o-, m-, and p-formylbenzoates O=CHC6H4CO2T (6) and the bis-(cycloheptatrienyl) dimer 7. The products from 11, (E)-15, and 21 are the bis(TEMPO) adducts (E,Z)-TOCH2CH= CHCO2T (12), (E,E)-TOCH2CH=CHCH=CHCO2T (17), and (E,Z)-CH2=C(OT)CH=CHCO2T (22), respectively.
- Tidwell, Thomas T.,Fenwick, Michael H.
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p. 3415 - 3419
(2007/10/03)
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- Ion pair acidities and aggregation of some amide and oxazoline enolates in THF
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Equilibrium lithium ion pair acidities at 25 °C have been determined in THF for the following acetamides: N,N-dimethyl-(4-biphenylyl)acetamide (1) (19.69), N,N-diethyl-(4-biphenylyl)acetamide (2) (20.30), N,N-dimethyl- diphenylacetamide (3) (20.76), N,N-diethyl-diphenylacetamide (4) (21.99), and 1-(diphenylmethylcarbonyl)pyrrolidine (5) (21.08). These acidity data compare well with those previously reported for the corresponding cesium enolates. Lithium and cesium ion pair acidities in THF are reported for two oxazolines: 2-(4-biphenylylmethyl)oxazoline (6) (Li, 21.53; Cs, 25.49) and (E)-(4S,5R)- 2-(4-biphenylylmethyl)-4-methoxymethyl-5-phenyloxazoline (7) (Li, 20.10; Cs 24.21). Studies of their acidities over a wide range of concentrations indicate that all of the lithium and cesium enolates of 1-7 are essentially monomeric at concentrations ranging from 10-3 to 10-4 M. Traces of dimer were detected for the lithium enolates of amides 1 and 2 and for the cesium enolate of oxazoline 6. Their dimerization constants (M-1) were found to be about 450, 200, and 150, respectively. All of the other lithium and cesium enolate probably form small amounts of dimer, but the dimerization constant of -1 is below the limit of precision of our spectroscopic method.
- Facchetti, Antonio,Streitwieser, Andrew
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p. 2281 - 2286
(2007/10/03)
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