Addition Reactions of Tertiary Silylphosphanes with Acetylenic Ketones and Aldehydes

Abstract

Trimethylsilyl)phosphanes Me 3 Si-PR 2 (PR 2 = PPh 2 , PEt 2 , 1-phospholanyl) add smoothly across the CºC bond of acetylenic ketones RCOCºCPh to form (Z)-3-phosphanyl-2-(trimethylsilyl)prop-2-en-1-ones 3 (3,4-addition). Thermal isomerization of the latter yields the corresponding 3-(trimethylsilyl)oxy-allenylphosphane 6, formally the product of a 1,4-addition. Mainly 1,2addition occurs with propiolic aldehydes leading to (1-[(trimethylsilyl)oxy]propargyl)phosphanes 4. Desilylation reactions of 3b yield either (3-oxopropyl)phosphanoxide 7 or (3-oxopropenyl)phosphanoxide 8.

Phospha-Michael reaction of tertiary phosphanes Ph2P–X (X=SiMe3, Cl) and N-triflyl-propiolamides

“…Also, protodesilylation can be achieved with various reagents and conditions [15,16]. As an example, we have reported earlier that vinylphosphane 5 (PEt 2 instead of PPh 2 ) underwent P oxidation and protodesilylation concomitantly when kept in aqueous acetone for several days [10]. In an effort to achieve an iododesilylation at the vinylsilane moiety, we allowed 4a, d, e to react with iodine chloride at rt and quenched the reaction with aqueous sodium thiosulfate (Scheme 3) [17][18][19][20].…”

“…Successful vicinal difunctionalization of alkynes by insertion of the C,C triple bond into the P-Si bond of tertiary silylphosphanes (e.g. Ph 2 P-SiMe 3 (1), Ph 2 P-SiMe 2 tBu), yielding trifunctionalized alkenes 2, has been achieved with several types of alkynes, such as alkoxyalkynes [9], acetylenic ketones [10] and esters [11] (Scheme 1). Notably, reactions with methoxy-or ethoxyacetylene and internal acetylenic ketones can be performed at room temperature.…”

P-Chirogenic silylphosphine-boranes: synthesis and phospha-Michael reactions

“…[19][20][21] Among the nucleophilic phosphorus reagents, the silylphosphines have recently retained the attention because these compounds are considered more electron-rich than the parent secondary phosphines due to the electrodonating effect of the silicon moiety. 22,23 Usually, the silylphosphines react with electrophiles through nucleophile-induced activation, 24,25 activated electrophile-driven reactions, [26][27][28][29] or using transition metal catalysis. [30][31][32][33] Thus, the silylphosphines 1 and 2 have been used for the stereoselective synthesis of MalPHOS 5 and Pchirogenic phosphines 6, by double phospha-Michael addition with the 2,3-dichloromaleic anhydride 3, 34 or Pd-catalyzed enantioselective arylation of the iodo compound 4, 35 respectively (Scheme 1a,b).…”