Acetylene‐Substituted Phosphane Oxides: Building Blocks for Macrocycles

Abstract

Phosphorus-based macrocycles with acetylenic scaffolds have been built from acetylene-substituted phosphane oxides that were formed from diisopropylphosphoramidic dibromide (3) and an acetylenic Grignard reagent. The fourand six-edged macrocycles 15 and 16, in which the iPr 2 NP(O) units are connected through 1,3-butadiyne rods, were obtained from the monosilylated derivative of iPr 2 NP(O)(C 2 H) 2 (7) by multiple acetylene coupling reactions under oxidative

Building blocks for phospha[n]pericyclynes

“…Oxidation of 11a with m-CPBA in CH 2 Cl 2 yielded phosphine oxide 12 (d( 31 P) À21.4) [17] after chromatography as a white crystalline solid (65%) that is stable for months when stored at À30°C. Stable sulfur analogue 13 was generated by reacting 11a with S 8 in CH 2 Cl 2 at 40°C and isolated as yellow crystals (53%) after chromatography.…”

“…However, the added stability intrinsically reduces the reactivity of the building blocks. For example, the oxide hampers the conversion of the amino-substituent into the third acetylene function [17], and the sulfide was found sensitive toward reduction in the reaction of P(S)Cl 3 with acetylides [22].…”

“…This report is an extension of recent work in which we examined the use of diethynylphosphine oxides toward 2-D pericyclyne formation [17]. In the present study, the amine substituent is addressed for its suitability in the synthesis and its potential for further substitution/replacement toward 3-D structures.…”

“…Reaction of i-Pr 2 NP(CBCH) 2 (11a) with HCl (0.1 M in Et 2 O) in diethyl ether at À10°C gave indeed immediate precipitation of i-Pr 2 NH AE HCl and 31 P NMR spectroscopy confirmed the quantitative formation of the desired chlorophosphine (18) (d( 31 P) 18.5), which was moderately stable below 0°C. For the related phosphine oxide 12, this facile substitution of the amino-group does not occur [17]. Chlorophosphine (18) is an attractive building block for the synthesis of functionalized triethynylphosphines and we reacted 18 with BrMg-CBCSiMe 3 to give phosphine (19a) (d( 31 P) À89.7) as the sole product (27%) after rapid filtration over silica gel.…”

“…of EtMgBr and subsequently reacted with 0.5 equiv. of i-Pr 2 NPCl 2 (10) to form triphosphine (17), confirmed by MS ([M+H] m/z 492.2; Scheme 8). The product mixture was shown to be very sensitive toward oxygen and silica gel and therefore not further purified.…”