Synthesis of 2,3-Dihydro-1-phenylbenzo[b]phosphole (1-Phenylphosphindane) and Its Use as a Mechanistic Test in the Asymmetric Appel Reaction: Decisive Evidence against Involvement of Pseudorotation in the Stereoselecting Step

Abstract

Racemic 2,3-dihydro-1-phenylbenzo[b]phosphole was obtained by reduction of 1-phenylbenzo[b]phosphole-1-oxide, itself derived by ring-closing metathesis of phenylstyrylvinylphosphine oxide. The title compound was then reoxidized under asymmetric Appel conditions. Comparison of the sense and degree of the stereoselectivity to those obtained with an open-chain analogue indicated that the ring system does not affect the selectivity of the process. This in turn strongly suggests that the stereoselection is not related to pseudorotamer preferences in putative phosphorane intermediates.

Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

“…More recent syntheses of the phospholene oxides involve either a ring-closing metathesis [35,[51][52][53][54], or a double Arbuzov reaction of 1,4-dichlorobut-2ene and a silylated P-reagent [34,35,55]. However, these syntheses generally afford the corresponding 3-phospholene oxides, and only a few examples are known to provide the corresponding 2-phospholene derivatives [56,57], which raises the necessity of complementary synthetic strategies for 2-phospholene oxides (Figure 1).…”

Phosphahelicenes with (Thio)Phosphinic Acid and Ester Functions by the Oxidative Photocyclisation Approach

“…Initial attempts carried out with PtO 2 /H 2 , l ‐selectride and NiCl 2 /NaBH 4 were ineffective, as they led to either recovery of the starting material or to decomposition. Finally, hydrogenation in the presence of 10 % Pd/C allowed obtention of the desired benzophospholene 5′ .…”

“…To access these substrates, we have sought conditions for the selective hydrogenation of the olefinic double bond of the P-MeO-phosphindole oxide 1'.I nitial attempts carriedo ut with PtO 2 /H 2 , l-selectride and NiCl 2 /NaBH 4 were ineffective, as they led to either recovery of the starting materialo rt od ecomposition. Finally,h ydrogenation in the presenceo f10% Pd/C [11] allowed obtention of the desired benzophospholene 5'.…”

Dynamic Cross‐Exchange in Halophosphonium Species: Direct Observation of Stereochemical Inversion in the Course of an SN2 Process

“…Generally, XPS with primary aliphatic or aromatic groups have average barriers of 10–12 kcal mol −1 in excellent agreement with our diastereomeric self‐exchange systems in the absence of branched alkyl groups . The fact that the reactivity of cyclic cation 10 is not significantly different from its close acyclic analogues 6 a and 7 is consistent with our earlier report of the similarity in the stereoselectivity in their respective DKR processes . However the introduction of the conformationally more strained dibenzophosphole moiety imposes a pronounced (ca.…”