Product studies of the photocycloaddition reactions of 5-chloro- and 5-fluorouracil derivatives and olefins. An interesting and useful effect of fluorine on regioselectivity

Abstract

earlier procedure. With the more reactive aromatics, p-dimethoxybenzene and naphthalene, additional competitions employing 2:1 or 5:1 molar ratios of benzene to p-dimethoxybenzene or naphthalene were also run.Peroxide-Initiated Reactions. Chloroacetonitrile, (5 mmol), toluene (10 mmol), and the peroxide (5 mmol) were dissolved in acetonitrile (100 mL), degassed with nitrogen, and heated. The OO-tert-butyl isopropyl peroxycarbonate reactions were refluxed (80 °C) for one week whereas the di-n-propyl peroxydicarbonate reactions were placed in a constant temperature bath at 60 °C for 6 h. In both cases iodometric analysis indicated that unreacted

Photochemistry of heterocycles: VIII. photocycloaddition of acetylenic compounds to 1,3-dimethyl-6-azathymine

“…But when acetone was added into the reaction system, the reaction rate was increased dis- Similarly, whether acetone was added to the reaction mixture or not, the reaction products obtained were the same. They were 2,4,6-trimethyl-3,5-dioxo-7,8-bismethoxymethyl-l,2,4-triazabicyclo[4,2,0]-7-heptene (2) and 1,3,5-trimethyl-4-oxo-8,9-bismethoxymethyl--2,3,5-triaza-7-oxaspiro[5,3]-1,8-nonadiene (3). When acetone was added into the mixture the reaction was much faster.…”

Kinetics and Mechanism of Photocycloaddition of Deoxyuridines to 2,3‐dimethyl‐2‐butene

“…On the other hand, however, photochemical reactions of pyrimidine bases and nucleosides with simple olefins, though it would provide a basis for understanding their photolability, have unexpectedly received little attention. In the literature, a few studies have been reported by Swenton et al 9,10 and Kaneko and Shimomura 11 who have compared these reactions with photocycloaddition of α,β‐unsaturated carbonyl compounds, and by Charlton and Lai 12 who have studied on the reaction of uridine with 2,3‐dimethyl‐2‐butene (Bu). † No one has investigated the mechanistic aspects of these reactions.…”

Explorations in crystal engineering

“…[193][194][195][196] Later efforts also considered photodimerization of 5-FU as a useful synthetic approach to substituted pyrimidines and novel bicyclic nucleosides (Scheme 4.2b). [197][198][199] The photophysics behind the dimerization [200][201] and cleavage 202 of fluorouracil dimers and cycloadducts was also studied as interest in 5-FU was maintained through the last few Continued efforts by the group moved from the original backbone to a polymethacrylatebased block copolymer, wherein one block contained alkyl-ester side chains to produce a largely hydrophobic region of the polymer, the other block bearing side chains appended with the 4-methylcoumarin moiety, drastically increasing the number of available binding sites for the API (Scheme 4.3). 204 The resulting polymer formed micelles in a water/THF co-solvent system and was conjugated to 5-FU under long-wave UV.…”

“…We note that UV-irradiation of 5-FU in solution produces photodimers only in the presence of a sensitizer, 196 while CPRs of 5-FU in solution are quite limited (e.g. coumarin) [197][198][199] yet are gaining interest in drug delivery. 202,204 Our goal to form a solid 227 with a photoreactive API such as 5-FU would also, thus, provide a unique entry to pharmaceutical cocrystals 228 wherein the covalentbond-forming photoreaction may be useful for pharmaceutical applications.…”