421-69-2Relevant academic research and scientific papers
Fluorinated butanolides and butenolides. Part 5. Synthesis and nucleophilic reactions of 3-chloro-2-fluoro-2-buten-4-olide as tetronic acid analogue. Conjugate addition of hard nucleophiles and vinylic halogen displacement with soft phosphorus nucleophiles
Paleta, Old?ich,Volkov, Andrei,Hetflej?, Ji?í
, p. 147 - 157 (2000)
3-Chloro-2-fluorobut-2-en-4-olide (13) and 2-fluorobut-2-en-4-olide (14) were prepared by a six step synthesis starting from 1,2-dibromo-1,2-dichloro-1,2-difluoroethane (5). UV-initiated addition of 5 to ethylene afforded 1,4-dibromo-1,2-dichloro-1,2-difluorobutane (6a) that was easily dehydrochlorinated to 4-bromo-3,4-dichloro-3,4-difluorobut-1-ene (7) and subsequently by chlorine addition to 1-bromo-1,2,3,4-tetrachloro-1,2-difluorobutane (10). Fuming sulfuric acid affected CH2-Br bond in 6a to afford 4-bromo-3,4-dichloro-3,4-difluorobutan-1-ol (8), while with 10 bearing stable terminal CH2-Cl group the reaction took place at the trihalomethyl group to give 2,3,4-trichloro-2-fluorobutanoic acid (11a). Its sodium salt (11b) cyclized in solution or thermally in the solid state to 2,3-dichloro-2-fluorobutan-4-olide (12) that by dehydrochlorination with tertiary amine gave new butenolide 13 or by didechlorination with zinc 2-fluorobut-2-en-4-olide (14). Hard nucleophiles as methanol and piperidine afforded products of conjugate addition, while soft phosphorus nucleophiles, triethyl phosphite or tributylphosphane, affected vinylic C-Cl and C-F bonds to give products of nucleophilic vinylic substitution.
Synthesis of 5-alkyl-3,4-difluorofuran-2(5H)-ones by lactonisation. Effects of substituents on cyclisation ability of fluorinated 4-hydroxyalkanoates. DFT calculations of the cyclisation energies
Hajduch, Jan,Duda, Zdeněk,Beran, Ji?í,Kví?ala, Jaroslav,Paleta, Old?ich
supporting information, p. 45 - 59 (2014/05/20)
5-Alkyl-3,4-difluorofuran-2(5H)-ones were synthesised starting with radical addition of ethers to methyl 2,3,3-trifluoroprop-2-enoate, followed by alkyloxy bond cleavage, acid-catalyzed lactonisation and dehydrofluorination. For a study of substituent effects on lactonisation, methyl 4-bromo-2-chloro-2- fluorodecanoate and 2-chloro-2-fluoro-4,4-dimethoxybutanoate based on radical additions of methyl 2-bromo-2-chloro-2-fluoroacetate to oct-1-ene or vinyl acetate were prepared. DFT calculations of the transition state energies of the exo-trig cyclisations confirmed the observation that the ring closure became more feasible with increasing number of alkyls at C4 of the fluorinated 4-hydroxyesters.
