Reactivity of (Phosphaalkenyl)metal Species:  Transmetalations and Reactions with Carbonyl Compounds

Abstract

The (phosphaalkenyl)lithium carbenoid (Z)-Mes*PdCClLi (2; Mes* ) supermesityl ) 2,4,6tri-tert-butylphenyl) was transmetalated with MgBr 2 , ZnCl 2 , and HgCl 2 to furnish the new (phosphavinylidene)metal carbenoids Mes*PdCClMX ((Z)-5a, MX ) MgBr; (E)-5b, MX ) ZnCl; (E)-5c, MX ) HgCl), while with 0.5 equiv of the metal halide, the bis(phosphaalkenyl)metal carbenoids (Mes*PdCCl) 2 M ((Z,Z)-6a, M ) Mg; (E,E)-6b, M ) Zn; (E,E)-6c, M ) Hg) were formed. Compounds 2 and 5a were reacted with carbonyl compounds under 1,2addition, leading to the β-phosphaallyl alcohols 7-10. Bromine-lithium exchange at -90 °C between (Z)-Mes*PdCBrSiMe 3 ((Z)-14) and n-butyllithium furnished (E)-/(Z)-Mes*PdCLiSiMe 3 ((E)-/(Z)-16; E:Z ) 1:1. Transmetalation of (E)-/(Z)-16 with MgBr 2 or ZnCl 2 furnished only the trans-metal isomer of Mes*PdCMXSiMe 3 ((Z)-18a, MX ) MgBr; (E)-18b, MX ) ZnCl). From (E)-/(Z)-16, a new access to the phosphaallene Mes*PdCdCPh 2 (20) was obtained by reaction with benzophenone.

Palladium-Catalyzed Arylation of a Sterically Demandinggem-Dibromophosphaethene

“…The stereochemistry of 5 a was characterized from the J PH constant using 1 H and 31 P NMR . The inversion of stereochemistry during the metalation process of 3 a is similar to that of several phosphavinyllithiums that contain heteroelements . On the other hand, the P=C skeleton of phosphavinyllithium prepared from 3 a would be affected by the aromatic substituent.…”

Phosphorus Centers of Different Hybridization in Phosphaalkene‐Substituted Phospholes

“…[ 17 ] After quenching the reaction mixture with methyl iodide and subsequent workup, Mes*P=CCH 3 Br ( 2 ) was obtained in good yields. [ 18 ] The 1,7-octadiyne motif can be introduced by using one of two procedures that basically differ in the alkyne source. In the first case, 2 is coupled with 1,7-octadiynemagnesium bromide in THF by using [Pd(dba) 2 ] (dba=dibenzylideneacetone) and PPh 3 under reflux conditions.…”

“…Hence, Mes*PCBr 2 ( 1 ) was treated with n BuLi at −120 °C in the Trapp mixture (THF/diethyl ether/pentane 4:4:1) for 30 min 17. After quenching the reaction mixture with methyl iodide and subsequent workup, Mes*PCCH 3 Br ( 2 ) was obtained in good yields 18. The 1,7‐octadiyne motif can be introduced by using one of two procedures that basically differ in the alkyne source.…”

Reactions of phosphavinyl Grignard reagents with aldehydes: synthesis, characterisation and further reactivity of β-phosphaallylic alcohols

“…A brief hint of this potential has come from previous work by Bickelhaupt et al who have examined the cross-coupling of a sterically hindered phosphavinyl Grignard reagent with aryl halides, 9 and the 1,2-addition reactions of the phosphavinyl magnesium carbenoid, [Mes*P=C(Cl)MgBr], Mes* ¼ C 6 H 2 Bu t 3 -2,4,6, with acetophenone and acetyl chloride which gave the expected bphosphaallylic alcohol and phosphaenone products. 10 Herein, we report our efforts to extend this work to the reactions of the less hindered Grignard reagents, 1, with mono-and dialdehydes. The further reactivity of generated b-phosphaallylic alcohols towards metal alkyls, amides and alkoxides has given a variety of unexpected results.…”