Between Oxirane and Phosphirane: The Spring‐loaded Oxaphosphirane Ring. Issue 4 (10th December 2020)

• Record Type: Journal Article
• Authors: Espinosa Ferao, Arturo; Rey Planells, Alicia; Streubel, Rainer
• Is Part Of: European journal of inorganic chemistry. Issue 4(2021)
• Page Start: 348
• Page End: 353
• Publication Date: 2020-12-10
• Subjects: Cleavage reactions -- Oxaphosphiranes -- Ring-opening reactions -- Strained molecules; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.202000881
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: Due to the potential interest of oxaphosphiranes in ring‐opening polymerizations, accurate ring strain energies (RSEs) of a wide variety of oxaphosphirane derivatives was computed, after validation of the optimization method by comparison with reported X‐ray structures. The parent oxaphosphirane exhibits a moderate RSE (22.44 kcal/mol) that is significantly enhanced by κ ‐P‐complexation (especially with boranes), the introduction of P=O or P + ‐Me groups as well as exocyclic double bonds at the ring carbon, such as 3‐methylene, 3‐imino and 3‐oxo functionalities. However, C3 alkyl substitution or pentacoordination at P in σ 5 λ 5 ‐oxaphosphirane does not lead to significant variation of RSE. Bicyclic spiro‐oxaphosphirane derivatives show an RSE decrease when the size of the spiro ring increases. A moderate linear correlation between RSE and G(r)/ρ(r) values calculated at the ring critical points and also with the relaxed force constant ( k 0 ) for the P−C bond is observed for most oxaphosphiranes. The possibility of ring‐opening polymerization by using better (anionic) nucleophiles in the initiation step can be foreseen from the exergonicity and relatively low barrier of the endocyclic C−O cleavage by nucleophilic attack of methanol, thus underlining the effect of the RSE as driving force compared to acyclic analogs. Abstract : Accurate ring strain energies for a wide set of oxaphosphirane derivatives were computed, allowing to establish factors enhancing strain, such as the increase of coordination number at P and the presence of exocyclic bonds or spiro‐fused rings at C. The high reactivity towards ring opening reactions by C−O bond cleavage is studied for a weak nucleophile such as MeOH as case in point, thus preparing ring opening polymerization studies.