Synthesis and cleavage reactions of some dibenzophosphole derivatives

Palladium-Catalyzed Synthesis of Dibenzophosphole Oxides via Intramolecular Dehydrogenative Cyclization

“…There are several methods to synthesize dibenzophospholes. , The most frequently used method is the reaction between 2,2′-dilithiated biaryls and PhPCl 2 followed by oxidation of the formed dibenzophospholes by air or H 2 O 2 . The following methods have also been reported: cyclization of 2-biphenylphenylphosphinic acids by intramolecular Friedel–Crafts reaction, treatment of triphenylphosphine oxide with 2 equiv of PhLi and successive oxidation of the formed dibenzophospholes, treatment of tetraphenylphosphonium bromide with lithium diethylamide followed by oxidation, thermolysis of m -terphenyldichlorophosphines, and Et 3 B- and O 2 -mediated radical cyclization of secondary phosphine oxides with a biphenyl group . Our new strategy for the synthesis of dibenzophosphole oxides is shown in Figure .…”

Synthesis of alkyldibenzophosphole 5-oxides

“…The organic layer was dried and evaporated, yielding a brown solid that was purified by column chromatography eluting with CH 2 Cl 2 -CH 3 OH, 96 : 4. The 5-methyl-5H-dibenzophosphole 5-oxide was isolated as a white solid (47 mg, 51%); mp 90-91 ЊC (from CH 2 Cl 2 ) (lit., 6 89-91 ЊC); ν max (film)/cm Ϫ1 3056 (arC-H s), 1175 (P᎐ ᎐ O s); δ H (CDCl 3 , 300 MHz) 7.87 (dddd, H 4 , 2H, J H-P 9.6, J H3-H4 7.5, J H2-H4 1.2, J H1-H4 0.9), 7.79 (dddd, H 1 , 2H, J H1-H2 7.8, J H-P 2.7, J H1-H3 0.9, J H1-H4 0.9), 7.59 (dddd, H 2 , 2H, J H1-H2 7.8, J H2-H3 7.5, J H-P 1.5, J H2-H4 1.2), 7.44 (dddd, H 3 , 2H, J H3-H4 7.5, J H2-H3 7.5, J H-P 3.6, J H1-H3 0.9), 1.85 (d, H 14 , 3H, J H-P 13.8); δ C (CDCl 3 , 75 MHz) 140.54 (d, C 10 , J C-P 21.5), 133.17 (d, C 2 , J C-P 1.8), 132.48 (d, C 12 , J C-P 103.2), 129.14 (d, C 4 , J C-P 11.0), 128.82 (d, C 3 , J C-P 9.7), 121.18 (d, C 1 , J C-P 9.7), 16.19 (d, C 14 , J C-P 70.7); δ P (CDCl 3 , 121 MHz) 37.23 (s); m/z (CI, NH 3 ) 215 (M ϩ 1, 84%), 232 (M ϩ 18, 100%); (EI) 214 (M ϩ , 35%), 199 (M ϩ Ϫ CH 3 , 100%).…”

Synthesis of π-Extended Dibenzophospholes by Intramolecular Radical Cyclization and Their Properties

“…Recently, π-extended phospholes have been applied in organic electronic devices such as light-emitting diodes and organic photovoltaic devices, and the potential utility of this class of compounds has led to the development of unique synthetic methods . For simple dibenzo­phos­pholes, several synthetic methods have been reported including intramolecular Friedel–Crafts type cyclization of 2-biphenyl­phenyl­phosphinic acid or aryldichloro­phosphines, the reaction of tetra­phenyl­phos­phonium bromide with lithium diethyl­amide, and the anionic intramolecular cyclization of triphenyl­phos­phine oxide with 2 equiv of phenyllithium . However, reports on the synthesis of π-extended dibenzophospholes are limited; available methods include palladium-catalyzed intramolecular dehydrogenative cyclization of hydrophosphine oxides and a 4-fold free-radical phosphonylation reaction of a tetrabromo- p -terphenylene or biphenyl­thiophene .…”