A Nontemplated Route to Macrocyclic Dibridgehead Diphosphorus Compounds: Crystallographic Characterization of a “Crossed‐Chain” Variant of in/out Stereoisomers

Abstract

Reactions of (O=)PH(OCH CH ) and BrMg(CH ) CH=CH (4.9-3.2 equiv; m=4 (a), 5 (b), 6 (c)) give the dialkylphosphine oxides (O=)PH[(CH ) CH=CH ] (2 a-c; 77-81 % after workup), which are treated with NaH and then α,ω-dibromides Br(CH ) Br (0.49-0.32 equiv; n=8 (a'), 10 (b'), 12 (c'), 14 (d')) to yield the bis(trialkylphosphine oxides) [H C=CH(CH ) ] P(=O)(CH ) (O=)P[(CH ) CH=CH ] (3 ab', 3 bc', 3 cd', 3 ca'; 79-84 %). Reactions of 3 bc' and 3 ca' with Grubbs' first-generation catalyst and then H /PtO afford the dibridgehead diphosphine dioxides (4 bc', 4 ca'; 14-19 %, n'=2m+2); P NMR spectra show two stereoisomeric species (ca. 70:30). Crystal structures of two isomers of the latter are obtained, out,out-4 ca' and a conformer ofin,out-4 ca' that features crossed chains, such that the (O=)P vectors appear out,out. Whereas 4 bc' resists crystallization, a byproduct derived from an alternative metathesis mode, (CH ) P(=O)(CH ) (O=)P(CH ) , as well as 3 ab' and 3 bc', are structurally characterized. The efficiencies of other routes to dibridgehead diphosphorus compounds are compared.

Structures and Dynamics of Secondary and Tertiary Alkylphosphine Oxides Adsorbed on Silica

“…The very clean phosphine oxides neededf or this study ( Figure 1) were obtained in 77-84 %y ields as described previously. [31] For 1-3,( EtO) 2 PHO was reacted with the corresponding Grignard reagentsB rMg(CH 2 ) x CH=CH 2 (x = 4-6) that were obtained from the commercially availableb romoalkenes. The diphosphine dioxides 4 and 5 were synthesized by deprotonating 3 with NaH, followed by reaction with Br(CH 2 ) 14 Br and Br(CH 2 ) 8 Br,r espectively.…”

“…The diphosphine dioxides 4 and 5 were synthesized by deprotonating 3 with NaH, followed by reaction with Br(CH 2 ) 14 Br and Br(CH 2 ) 8 Br,r espectively. [31]…”

“…Phosphine oxides are also important synthetic intermediates and targets. [31,32] Phosphine oxidesf orm stable hydrogen bonds with diverse types of donors. Examples include phenols, which can be used to create extended assemblies of interest in materials science, [33,34] as well as naphthol, [35] sulfonic acids, [36] and water.…”

“…[21,37] The ability of phosphine oxidest of orm hydrogen bonds with silanols, phenols, and even chloroform has recently been illustrated. [23] Furthermore, the influence of hydrogen bondingo nt he 31 Ps olid-state NMR spectra of phosphine oxides has been analyzed in detail. [21,22,38,39] Recently,w ed iscovered that phosphine oxidesa lso possess the unique ability to stabilize hydrogen peroxidea nd di(hydroperoxy)alkanes by forming strong hydrogen bonds.…”

“…This could have implications for syntheses involving secondary phosphine oxides. [31,32] Third, it has never been investigatedw hether the simultaneous adsorptiono fasecond intramolecular phosphine oxide group would impede the overall mobility of an adsorbed diphosphine dioxide.…”