Alkyl with phosphines

Kyba and eoworkers prepared the similar, but not identical compound, 26, using quite a different approach. In this synthesis, pentaphenylcyclopentaphosphine (22) is converted into benzotriphosphole (23) by reduction with potassium metal in THF, followed by treatment with o "t/20-dichlorobenzene. Lithium aluminum hydride reduction of 23 affords l,2-i>/s(phenylphosphino)benzene, 24. The secondary phosphine may be deprotonated with n-butyllithium and alkylated with 3-chlorobromopropane. The twoarmed bis-phosphine (25) which results may be treated with the dianion of 24 at high dilution to yield macrocycle 26. The overall yield of 26 is about 4%. The synthetic approach is illustrated in Eq. (6.16), below. 

A water-soluble phosphine derivative of diazepam allows for more convenient parenteral tranquilizer therapy and avoids some complications due to blood pressure lowering caused by the propylene glycol medium otherwise required for administration. Fosazepam (82) is prepared from benzodiazepine by sodium hydride-mediated alkylation with chioromethyldimethyl phosphine... 

The osmium(VI) complexes 0s02X2(PR3)2 are not generally obtainable with the smaller alkyl and alkyl(aryl)phosphines, which tend to be good... 

In 6.5.2.1 it is shown that BF3 and BCI3 add to phosphine Pt complexes without cleaving the B—X bond. In contrast, aryl and alkyl boron halides are added oxidatively with phosphine Pt complexes - ... 

Both MeMn(CO)5 and PhMn(CO)5 react with acetylenes to yield vinyl ketone tetracarbonyl complexes, most likely via a pathway involving CO insertion [Eq. (18)] 14, 36). Reactions of these same alkyls with 1,3-dienes may proceed similarly 16, 95, 96). The chelating ligand o-styryldiphenyl-phosphine (L—L) converts MeMn(CO)j into two products 25) whose structures (XXII and XXIII) were elucidated by X-ray crystallography 24). An unusual migration of COMe onto L—L occurs subsequently to the initial insertion step. 

O-Bond metathesis of the Ln-alkyl with the phosphine gives a Ln-phosphido complex. (This initiation step was observed to be faster when the hydride derivative [Cp 2bnH]2 was used.) Since the reactions were zero-order in substrate, the next... 

Scheme 10.91 Grignard crosscoupling of 1-phenylethylmagnesium chloride and vinyl bromide with S-alkylated amino phosphine ligands.

Simple ketones react with PH3 in strongly add media to form primary phosphine oxides and 1-hydroxy alkyl-sec. phosphine oxides... 

The phosphine oxide (-)-(5 )-[2-(dimethylamino)ethyl]methyloxophenylphosphorane85 was treated with butyllithium or LDA to give, via directed lithiation, the methylene-deprotonated compound regioselectively. Alkylation with bromomethylbenzene gave (S)-[l-benzyl-2-(di-methylamino)ethyl]methyloxophenylphosphorane with low diastereoselectivity (d.r. 55 45)86. 

Pioneering studies with trialkylphosphines by Fu and coworkers88 and with dialkylarylphosphines by Buchwald and coworkers89 have provided solutions to many pending problems of the Pd-catalyzed cross-coupling, such as those shown in Scheme 26. Applications of bulky alkyl-containing phosphines are further discussed also in later sections. 

Rather unexpectedly, the reaction product of alkenylzirconocene chlorides can be alkylated with primary alkyl bromides under the influence of a catalyst-solvent system consisting of 2.5% Pd(acac)2, 2 equiv. LiBr and 1 1 THF-NMP without any phosphine and NMI used above881 (Scheme 77). 

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