Benzophenone, directed reaction with

Benzophenone, directed reaction with acetaldehyde, 50, 68 1,4-Benzoquinone, 2,3-dichloro-5,6-dicyano-, (DDQ), aroma-tization with, 54, 14 Benzoylacetone, from acetophenone and acetic anhydride,... 

Benzophenone, directed reaction with acetaldehyde, 50,68 Benzoylacetone, from acetophenone and acetic anhydride, 51, 93... 

The PFR of A-chloroacetylanthranylates afford benzophenones, whose direct reaction with ammonia gives 1,3-quinazolines. Alternatively, treatment with potassium iodide before addition of ammonia leads to l,3-dihydro-2ff-l,4-benzodiazepin-2-ones [178]. A related synthesis of benzodiazepines is based on an initial PFR of anilides derived from ALBoc-Ala-OH (Scheme 31.18) [179]. 

With m-nitroanisole in liquid ammonia the benzophenone-sensitized reaction yields inter alia 2-methoxy-4-nitroaniline as a product and no m-nitroaniline, which is formed in very high yield upon direct irradiation in liquid ammonia as well as in NH3/CH3OH. In the latter instance l/4> varies linearly with 1/[NH3], suggesting that the reaction is either singlet or triplet but not of a mixed type. 

In the direct effect of ionizing radiation on DNA, radical cations are the primary products (Chap. 12). For this reason, their reactions are of considerable interest. Obviously, photoionization (e.g., at 193 nm) and laser multi-photon excitation leads to such species (e.g., Candeias and Steenken 1992b Malone et al. 1995 Chap. 2.2). Base radical cation electron pairs have been proposed to be the first observable intermediates with a lifetime of 10 ps for Ade and four times longer for the other nucleobases (Reuther et al. 2000). Radical cations are also assumed to be intermediates in the reactions of photosensitization reactions with qui-nones, benzophenone, phthalocyanine and riboflavin (Cadet et al. 1983a Decar-roz et al. 1987 Krishna et al. 1987 Ravanat et al. 1991, 1992 Buchko et al. 1993 Douki and Cadet 1999 Ma et al. 2000). Nucleobase radical cations may be produced by electrochemical oxidation (Nishimoto et al. 1992 Hatta et al. 2001) or with strongly oxidizing radicals (for a compilation of their reduction potentials see Chap. 5.3). Rate constants are compiled in Table 10.3. 

Thioxanthone dioxide itself has been prepared directly from benzophenone by a double electrophilic substitution reaction with chlorosulfonic acid (Equation 190) <1995JCX321>. 

Quaternary Ammonium Salt-Mediated Asymmetric Direct Aldol Reaction of Glycinate Benzophenone Schiff Base with 3-Phenylpropanal Under Phase-Transfer Conditions [6] (p. 145)... 

Cytochrome P-450 can perform both intramolecular and intermolecular nitrene insertions with 106 in water solution [181]. However, the intermediate metallo-nitrene (108) also hydrolyzed to some extent so the enzyme performed a hydroxylation as well as an amidation. Although we have also performed an intermolecular amidation of a steroid, using such a metalloporphyrin reaction with 106 to form 112 [182], we have not yet extended it to the kinds of directed functionalizations described above with either benzophenones or chlorinations. 

Diaryl ketimines, Ar1C=NH. The patent literature has described the preparation of (C6H5)2C=NH by direct reaction of benzophenone with ammonia, but this route has not been investigated further. Actually, a number of diaryl ketimines can be obtained in >95% yield by reaction of a diaryl ketone with liquid ammonia and a catalytic amount of ammonium chloride in THF in a sealed tube at 120° (60 bar). 

Photoreduction of benzophenone by primary and secondary amines leads to the formation of benzpinacol and imines [145]. Quantum yields greater than unity for reduction of benzophenone indicated that the a-aminoalkyl radical could further reduce the ground state of benzophenone. Bhattacharyya and Das confirmed this in a laser-flash photolysis study of the benzophenone-triethylamine system, which showed that ketyl radical anion formation occurs by a fast and a slow process wherein the slow process corresponds to the reaction of a-aminoalkyl radical in the ground state of benzophenone [148]. Direct evidence for similar secondary reduction of benzil [149] and naphthalimides [150] by the a-aminoalkyl radical have also been reported. The secondary dark reaction of a-aminoalkyl radicals in photo-induced electron-transfer reactions with a variety of quinones, dyes, and metal complexes has been studied by Whitten and coworkers [151]. 

The photolysis of diazomethane at 4360 and 3650 A was investigated by Nor-rish, who found (N2) 4 and methylene was postulated as the intermediate. Spin conservation rules require that methylene be formed in a singlet state, but rapid decay to the ground triplet occurs and much of the controversy in the literature centers on the spin state of methylene prior to chemical reaction with a double bond . The benzophenone or Hg( Pi) sensitized decompositions of diazomethane yields triplet methylene directly, presumably via electronically-excited (triplet) diazomethane . Recently it has been shown that triplet methylene can be formed in the photolysis of diazomethane at longer wavelengths by intersystem crossing , viz. 

---