Tri-tert-butyl phosphine

Some breakthrough was finally achieved by using Pd2(dba)3 as the Pd complex, tris(tert-butyl)phosphine as the ligand, and sodium ferf-butoxide as the base [90]. This combination of reagents proved to bring about the synthesis of unsubstituted phenazine (137) by reaction of two molecules of 2-bromoaniline (131). Remarkably, no reaction takes place under the conditions of the 133 117 transformation. Currently the scope and limitations of this new sequential inter-Zintramolecular AT-arylation for the synthesis of AT-heterocycles... 

Table 10. H-NMR spectra of stereoisomeric 4-hydroxy-2.4.6-tri-tert-butyl-phosphinic acid methylesters 84 E and 84 Z 6 in ppm, CDCI3 solvent)...

Fig. 24. Mass spectrum of Z-2.4.6-tri-tert-butyl- -phosphinic acid methyl ester...

In 1998, Miyaura reported a Rh(acac)(CO)2/dppp-catalyzed addition of aryl or alkenylboronic acids to aldehydes in aqueous organic mixtures under an inert atmosphere (Eq. 8.85). The use of electron-rich tri(tert-butyl)phosphine as ligand was found to be beneficial for obtaining good yields of the corresponding aldehyde addition products. ... 

Tri- tert-butyl-1,3,5 -triphosphabenzene (128, Scheme 53) undergoes a ring contraction over a potassium mirror,159 with the elimination of potassium phosphine and formation of the aromatic 2,4,6-tri-tot-butyl-1,3-diphosphacyclopentadienide anion 129 with three bulky substituents (Scheme 53). The driving force of this reaction could be the higher aromaticity of the five-membered ring. 

Tri-tert-butylphosphine Phosphine, tri-tert-butyl- (8) Phosphine, tris(1,1 -dimethylethyl)- (9) (13716-12-6)... 

Tri-tert-butyl-X -phosphorin24 readily reacts with bromine and with chlorine. Mach oxidizing with bromine in CCI4, could not isolate a crystalline product. The brown colour of the addition product of one mole Br2 to one mole 24 disappeared with water and the crystalline 2-hydro-phosphinic acid 85b could be isolated in 45% yield. Methyl-magnesium-iodide or red phosphorus yielded 2.4.6 tri-tert-butyl-X -phosphorin 24. It seems reasonable to suppose that on bromination l.l-dibromo-2.4.6-tri-tert-butyl-X -phosphorin was formed. 

Mach isolated a crystalline stericaUy uniform substance, m.p. 77-78,5 °C, identified as 4-chloro-phosphinic acid chloride 94. 1.1.1.4-Tetra-chloro-2.4.6-tri-tert-butyl-X -phosphorin 93 is assumed to be the primary chlorination product. 

Completely different results from those obtained in the photooxidation of 2.4.6-tri-tert-butyl-X phosphorin 24 (p. 54) are obtained in the photooxidation of 1.1-dimethoxy-2.4.6-tri-tert-butyl-X -phosphorin 183, as Schaffer has found. In this case the 2-hydroxy-endoxy-phosphinic acid methyl ester 213 can be isolated in about 20% yield. Its formation can be explained by assuming normal 1.4-addition to 212 as the primary product which is transformed to 213 by hydrolytic ring cleavage of the peroxide bridge, followed by loss of methanol. 

QiHjiOjP, Tris(4-methylphenyl) phosphite ruthenium complex, 26 277, 278 C2 H3,PSi, Phosphine, (2,4,6-tri-tert-butyl-phenyl)(trimethylsilyl)-, 27 238 QsHaiNOP, Benzamide, 2-(diphenylphos-phino)-W-phenyl-, 27 324... 

Desulfurization with tri(n-butyl)phosphine converts both fc(S3) (or its tert-butyl-substituted derivatives) [273, 274] and [Fe(C5H3)2](S3)2 (or its tert-butyl-substituted analog) [272] to polymers in which the ferrocene units are linked through disulfide bridges (cf. Sect. 5.8). 

SiPCjiHw, Phosphine, (2,4,6-tri-tert-butyl-phenyl)(trimethylsilyl) -, 27 238... 

Almost all Suzuki polycondensations published to date in the literature use 1-3 mol% of catalyst, mostly Pd[P(p-tolyl)3]3, Pd(PPh3)4 or in situ prepared Pd[P(o-tolyl)3]2. Most catalysts for the Suzuki polycondensation employ tri-arylphosphine ligands. New ligands, which include Buchwald s biaryl-based phosphines, Beller s diadamantyl phosphines, Fu s tri(tert-butyl)phos-phine, and Hartwig s pentaphenylated ferrocenyl phosphines, have been developed for Suzuki-Miyaura cross-coupling reactions. Buchwald-type ligand has been applied to polymerize dichloro monomers using Suzuki polycondensation. 

Scheme 1 Synthetic steps for compounds 1 and 2.1 2-chloroacetic acid, 2 M aq. Na2C03, 80 °C, 20h, yield 51% 11 acetic anhydride, anhydrous sodiiun acetate, 60 °C, 5h, yield 65% 111 sodium sulfite, H2O, 90 °C, 4h, yield 82% IV toluene/piperidines, reflux 4h, yield 61% V tert-butyl acrylate, tri-(0-tolyl)phosphine, Pd(OAc)2, EtsN, DMF, reflux, yield 70-91% VI H2, 10% Pd/C, rt, yield 96-100% Vll TFA, DCM, rt, yield 75-100% Vlll (a) isobutylchloroformate, EtsN, dry DCM, 0°C, (b) R2NH, DCM, rt, 62-70% IX UAIH4, dry THF, yield 24-44% [11]...

Larger chalcogen-phosphorus heterocycles, although less common in the literature, are accessible via a variety of synthetic routes.2,83,84 For example, the cyclic trimer (SPR)3 (R = 2,4,6-tri-tert-butylphenyl) contains a puckered six-membered P3S3 ring and is produced in the reaction of a phosphinic chloride with lithium sulfide (Equation 73).98 Additionally (R P)3Se5 (R = 2,4-di-tert-butyl-6-wopropoxyphenyl), synthesised from the oxidation of a primary phosphine with three equivalents of elemental selenium (Equation 74), has... 

Synthesis of (-I-) calanolide A (Scheme 8-11) was achieved by enzyme catalyzed resolution of the aldol products ( )-53. Compound 7 with acetaldehyde by aldol reaction in the presence of LDA/TiCU stereoselectively produced a mixmre of ( )-53 and ( )-54 (94% yield), the ratio of which was 96 4. ( )-53 was then resolved by lipase AK-catalyzed acylation reaction in the presence of tert-butyl methyl ether and vinyl acetate at 40 °C to obtain 41% yield of (+)-55 and 54% yield of the acetate (—)-56. Mitsunobu cyclization of (+)-55 in the presence of tri-phenylphosphine and dielthyl azodicarboxylate afforded 63% yield of (-l-)-43 with 94% ee as determined by chiral HPLC. Luche reaction on (+)-43 with CeCla 7H2O and triphenyl phosphine oxide and NaBH4 in the presence of ethanol at 30 °C gave the crude product. It was purified by column chromatography on silica gel to give 78% yield of a mixture containing 90% of (+)-calanolide A and 10% (+)-calanohde B, which were further separated by HPLC. 

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