- Combinatorial Nickel-Catalyzed Monofluoroalkylation of Aryl Boronic Acids with Unactivated Fluoroalkyl Iodides
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A combinatorial nickel-catalyzed cross-coupling between arylboronic acids and unactived 1-fluoro-1-iodoalkanes has been developed, which demonstrated high efficiency, mild conditions, and excellent functional-group compatibility. Readily available nitrogen and phosphine ligands were combined with a nitrogen source, which in situ generated a variety of easily tunable catalysts to promote the fluoroalkylation for broad scopes of both coupling partners. This new strategy on combinatorial catalysis offers new solutions for nickel-catalyzed cross-coupling reactions.
- Sheng, Jie,Ni, Hui-Qi,Liu, Ge,Li, Yan,Wang, Xi-Sheng
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supporting information
p. 4480 - 4483
(2017/09/11)
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- Nickel-catalyzed monofluoromethylation of aryl boronic acids
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Aryl boronic acids can be monofluoromethylated under nickel catalysis. The utility of this method is demonstrated by the monofluoromethylation of a borylated and acyl-protected derivative of the statin drug ezetimibe. Mechanistic investigations indicate that a fluoromethyl radical is involved in the NiI/NiIII catalytic cycle.
- Su, Yi-Ming,Feng, Guang-Shou,Wang, Zhen-Yu,Lan, Quan,Wang, Xi-Sheng
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supporting information
p. 6003 - 6007
(2015/05/13)
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- Studies toward the synthesis of α-fluorinated phosphonates via tin-mediated cleavage of α-fluoro-α-(pyrimidin-2-ylsulfonyl) alkylphosphonates. Intramolecular cyclization of the α-phosphonyl radicals
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Treatment of the α carbanions generated from several α-(pyrimidin-2-ylsulfonyl)alkylphosphonates with Selectfluor gave high yields of the α-fluoro-α-(pyrimidin-2-ylsulfonyl)alkylphoshonates, which were desulfonylated [Bu3SnH/2,2'-azobisisobutyronitrile (AIBN)/benzene or toluene/Δ to give α-fluoroalkylphosphonates. "Catalytic" tin hydride, generated from tributyltin chloride and excess polymethylhydrosiloxane in the presence of potassium fluoride, also effected removal of the π-deficient α-(pyrimidin-2-ylsulfonyl) group from the phosphonate esters. Substitution of Bu3SnD for Bu3SnH gave access to α-deuterium-labeled phosphonates. Prolonged treatment of α-(pyridin-2-ylsulfonyl)alkylphosphonate with excess Bu3SnH/AIBN or catalytic tin hydride also effected desulfonylation but in moderate yields. This represents a mild new methodology for removal of the synthetically useful π-deficient heterocyclic sulfone moiety and an alternative route for the preparation of α-fluorinated phosphonates. Desulfonylation is suggested to proceed via attack of tin radical at an oxygen (or sulfur) atom of the sulfonyl group to give a stabilized α-phosphonyl radical intermediate. The latter was found to undergo 5-exo-trig ring closure to give the corresponding 2-methylcyclopentylphosphonates. Treatment of diethyl 1-bromohex-6-enylphosphonate with Bu3SnH/AIBN produced an analogous mixture of ring-closure products. Treatment of [(2-bromo-5-methoxyphenyl)(fluoro)(pyrimidin-2-ylsulfonyl)]methylphosphonate with Bu3SnH resulted in an intramolecular radical [1,5]-ipso substitution reaction and migration of the pyrimidinyl ring to give fluoro[5-methoxy-2-(pyrimidin-2-yl)phenyllmethylphosphonate.
- Wnuk, Stanislaw F.,Bergolla, Luis A.,Garcia Jr., Pedro I.
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p. 3065 - 3071
(2007/10/03)
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