Preparation and Reactions of 1,3‐Diphosphacyclobutane‐2,4‐diyls That Feature an Amino Substituent and/or a Carbonyl Group

Abstract

The preparation and properties of a 1-amino-1,3-diphosphacyclobutane-2,4-diyl and a 1-benzoyl-1,3-diphosphacyclobutane-2,4-diyl, which can be regarded as functionalized cyclic biradical derivatives, were investigated. Hydrolysis of 1-diisopropylamino-3-methyl-2,4-bis(2,4,6-tri-tert-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyl (7), which is formed by reaction of Mes*C[triple chemical bond]P (4; Mes*=2,4,6-tBu(3)C(6)H(2)) with lithium diisopropylamide and iodomethane, resulted in ring-opening of the 1,3-diphosphacyclobutane-2,4-diyl skeleton, as well as de-aromatization of one of the Mes* rings. 3-Oxo-1,3-diphosphapropene 8 and 7-phosphabicyclo[4.2.0]octa-1(8),2,4-triene 9 were the resultant products, and these were subsequently characterized. Isomerization and oxidation of 7 occurred in the presence of TEMPO (2,2,6,6-tetramethyl-1-piperidinoxy) to give the first example of a cyclic dimethylenephosphorane derivative, namely 3-oxo-1,3-diphospha-1,4-diene 10. 1-Benzoyl-3-tert-butyl-2,4-bis(2,4,6-tri-tert-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyl (12) was isolated and characterized from the reaction of 4 with tert-butyllithium and benzoyl chloride. Compound 12 was subsequently heated and underwent rearrangement of the benzoyl group and ring-expansion to afford 1-oxo-1H-[1,3]diphosphole 13. Reaction of 4 with lithium diisopropylamide and benzoyl chloride afforded the 2H-[1,2,4]oxadiphosphinine 15, which was probably formed through the 1,3-diphosphacyclobutane-2,4-diyl intermediate 14. Thermolysis of 15 afforded 1-oxo-1H-[1,3]diphosphole 16 in an Arbuzov-type rearrangement.

Dual Supermesityl Stabilization: A Room‐Temperature‐Stable 1,2,4‐Triphosphole Radical, Sigmatropic Hydrogen Rearrangements, and Tetraphospholide Anion

“…[1] It has been shown that the reaction between simple tris(trimethylsilyl)phosphane (2), as a source of phosphorus, and 2,4,6-tri-tert-butylbenzoyl chloride (3) does not take place at room temperature. More active metal bis(trimethylsilyl)phosphides, e.g., lithium bis(trimethylsilyl)-phosphide, are required for the reaction to take place.…”

“…The introduction of two supermesityl groups has been recently shown to stabilize such intriguing diradicals as 5-7 and the diphosphorus analogue 8 of a cyclic carbene (Scheme 1). [3][4][5] …”

Preparation and X-ray analyses of siloxane-bridged acyclic and 8-membered cyclic phosphaethenes

“…A dibromophosphaethene 2 [19] was allowed to react with butyllithium and phosphaethenyllithium 1 thus generated was treated with a half of equivalent amount of dichlorodisiloxane to give 3 in a moderate yield (Scheme 1). The NMR data suggested a highly symmetrical structure: 31 P NMR spectrum showed a single peak for the Mes * P@C(Br)SiMe 2 moiety, which was also supported by 1 H and 13 C NMR spectroscopy.…”

“…Structure solution, refinement, and graphical representation were carried out using the TEXSAN package [29]. Compound 2 was prepared according to the literature [19].…”

Access to Air‐Stable 1,3‐Diphosphacyclobutane‐2,4‐diyls by an Arylation Reaction with Arynes

“…[8] Next, conditions for the generation of benzyne were examined (Table 1). At first, ac ombination of o-bromophenyl triflate and an alkyl lithium [9] was used in THF at À78 8 8C, but the reaction gave an unidentified mixture (Table 1, entry 1).…”