Wittig-olefination via an yttrium-coordinated betaine

Abstract

We report the synthesis of an yttrium phosphonium methylide complex and its reaction with benzophenone to form an excedingly rare hydrocarbon soluble metal-coordinated betaine. While this reaction models the C-C r-bond formation step of the Wittig reaction under salt-conditions, addition of Ph 3 PQ Q QO to the betaine complex results in formation of 1,1-diphenylethene. Scheme 1 Wittig-olefination of an aldehyde by [CH 2 PPh 3 ].

Unusual Fragmentation and Transformation of an N‐Heterocyclic Carbene by a Stable Phosphonium–Borane peri‐Functionalized Naphthalene

“…The crystal structure of ylide 5 was determined by X‐ray diffraction analysis and is shown in Figure . The CH 2 group in ylide 5 displayed a sharp doublet at 0.83 ppm in the 1 H NMR spectrum, whereas the phosphorus atom produced a singlet peak at 21.0 ppm in the 31 P{ 1 H} NMR spectrum, which is comparable to other Ph 3 P=CH 2 species . The P=CH 2 bond length of ylide 5 was 1.652(8) Å/1.649(8) Å (for the two independent molecules), which is typical of phosphine ylides, and the P⋅⋅⋅B separation distance (6.91(1) Å) was much longer than those in compounds 3 and 4 .…”

“…The CH 2 group in ylide 5 displayed as harp doublet at 0.83 ppm in the 1 HNMR spectrum, whereas the phosphorus atom produced as ingletp eak at 21.0 ppm in the 31 P{ 1 H} NMR spectrum, which is comparable to other Ph 3 P=CH 2 species. [21] The P=CH 2 bond length of ylide 5 was 1.652(8) / 1.649(8) ( for the two independent molecules), which is typical of phosphine ylides, [17] and the P···B separation distance (6.91(1) ) was much longert han those in compounds 3 and 4.U pon the addition of IMe to ylide 5,w eo bserved ad istinct peak at À9.7 ppm in the 11 B{ 1 H} NMR spectrum, which is similar to that of the IMe adduct 3,w hereas the 31 Pc hemical shift experienced negligible change (21.6 ppm). From the NMR data, a1:1 IMe adduct with ylide 5 (designated as compound 6)w as determined to form quantitatively( Scheme 3);t he crystalso f compound 6 were highly air sensitivea nd too small forX -ray diffraction analysis.…”

Potassium and Yttrium Complexes of a Rigid Bis‐Phosphido POP‐Donor Ligand

“…The Y–I distance of 2.964(1) Å in 3 is also within the range previously reported for yttrium iodido compounds. For example, the Y–I distances are 2.9287(3) and 2.9464(3) Å in [{HC(CMeNAr) 2 }YI 2 (THF)], 2.947(1)–2.979(1) Å in [Y{P(SiMe 3 )Ar}I 2 (thf) 3 ] (Ar = 2,6‐C 6 H 3 i Pr 2 ), and 3.0161(8) Å in [YI{N(SiMe 3 ) 2 } 2 (CH 2 PPh 3 )] . The Y–O THF distances of 2.322(5) and 2.336(5) Å are typical,, whereas the Y–O(1) distance of 2.508(4) Å is substantially elongated, reflecting the poor donor ability of a diarylether ligand, combined with steric constraints imposed by the rigidity of the XP 2 pincer ligand framework.…”

Making natural products from renewable feedstocks: back to the roots?

“…160 Quinones A 57 and F 58 were accessed by epimerization of aldehyde 54 followed by oxidation (taiwaniaquinone F ( All four natural products synthesized occur in the same plant species. 163 Methylenetriphenylphosphorane (50) was prepared from triphenylphosphine and iodomethane, 164 available from methanol (wood spirit) and HI. 165 Iododiene 51 can be prepared in three steps from 6methylhept-5-en-2-one, which can be isolated from several plant species.…”