The phosphinoboration of carbodiimides, isocyanates, isothiocyanates and CO₂

Abstract

The transition metal-free addition of phosphinoboronate ester PhPBpin (pin = 1,2-OCMe) to heterocumulenes including carbodiimides, isocyanates, isothiocyanates and carbon dioxide has been investigated. The corresponding 1,2-addition products were readily prepared at room temperature without the need of a catalyst or added base. Addition of methanol to the compounds derived from addition of PhPBpin to carbodiimides, isocyanates, and isothiocyanates resulted in traditional hydrophosphination products. The methodology developed in this study provides a simple and elegant route for the generation of a wide range of functionalized phosphines. The phosphinoboronate ester PhPBpin also selectively and reversibly adds to CO at room temperature in a 1,2-manner.

α‐Borylated Phosphorus Ylides (α‐BCPs): Electronic Frustration within a C−B π‐Bond Arising from the Competition for a Lone Pair of Electrons

“…In case of addition of PhNCO to 1,t he resulting molecule 6 even hasavery similars tructural motif to the postulated FLP structureo ft he "confused" Lewis pair reported by Grimme and Warren et al [24] It also has to be noted that the reactivity of 1 with the (hetero)cumulenes X=C=Yi ss imilart ok nown P/Bbased FLP systems and systemsw ith adjacent p-orbitals like the phosphinoboronate ester Ph 2 PBpin (pin = 1,2-O 2 C 2 Me 4 )r eported by Stephan and Westcott et al [25] Overall, the presented a-borylated phosphorus ylide (a-BCP) demonstrates that it is indeed possible to generate frustration or at least ah ighly polarized, very reactive bond in aC /Bbased p-bond by "restraining" the electron pair by competition for the lone pair of electrons. This is emphasized by the fact that reactivity of 1 with CO and other small molecules is found, even thoughn oe lectron-withdrawings ubstituents at the boron atom or ring strain effects are employed.…”

Double Phosphinoboration of CO2: A Facile Route to Diphospha‐Ureas

“…[21] Subsequently,W estcott and co-workersr eported relateda ddition reactions in which Ph 2 PBpin reacts with unsaturatedm ultiple bonds prompting phosphinoboration of ketones, imines, aldehydes, [22] N-heterocycles, [23] and as eries of heteroallenes. [24] In the present study,w ed escribe the reactionso fC O 2 with as eries of phosphinoboranes,d emonstrating that suitable modification of the B/P reagent prompts CO 2 reduction to afford au nique and facile route to diphospha-ureas. Computationals tudies provide insighti nto the mechanism,r evealing an intermediate derived from double phosphinoboration of CO 2 .…”

“…[17] Subsequently,t he reduction of dimericp hosphaketenes, RPCO was reportedt og ive an alternativer oute to ad iphospha-urea. [24] In the present study,w ed escribe the reactionso fC O 2 with as eries of phosphinoboranes,d emonstrating that suitable modification of the B/P reagent prompts CO 2 reduction to afford au nique and facile route to diphospha-ureas. [20] In targeting new strategies to CO 2 reductiont od iphospha-ureas, we note that we had some time ago reported the reactions of the phosphinoboranes R 2 PB(C 6 F 5 ) 2 with H 2 through aFLP-typer eaction.…”

“…[24] Based on the spectroscopy alone, the compound was formulated as Ph 2 PCO 2 Bpin 1 (Scheme 1). [24] Based on the spectroscopy alone, the compound was formulated as Ph 2 PCO 2 Bpin 1 (Scheme 1).…”

“…We previously described the stoichiometric reactiono f Ph 2 PBpin with CO 2 . [24] Based on the spectroscopy alone, the compound was formulated as Ph 2 PCO 2 Bpin 1 (Scheme 1). Repetitiono ft he reactiona fforded X-ray quality crystals and the subsequentd iffractions tudy confirmed the formulation (Figure 1).…”