Lithium 0,0-diethyl

These reactions can be carried out catalytically because the tellurium precipitated during the deoxygenation of the oxiranes will react rapidly with added sodium diethyl phosphite. Lithium 0,0-diethyl tellurolophosphate is a more powerful deoxygenation reagent and is able to convert certain internal epoxides to olefins in a stereospecific manner3. 

To complement the above information, a highly enantioselective synthesis of a-amino phosphonate diesters should be mentioned.164 Addition of lithium diethyl phosphite to a variety of chiral imines gives a-amino phosphonate with good to excellent diastereoselectivity (de ranges from 76% to over 98%). The stereoselective addition of the nucleophile can be governed by the preexisting chirality of the chiral auxiliaries (Scheme 2-63). 

Various diboriodilithiomethanes of type 225 were synthesized by Bemdt and coworkers, adding different aryllithium compounds to the boron-carbon bonds of compounds 224a-e (Scheme 77) . The dilithium compounds have been characterized in the solid state by X-ray structural analysis. 225a-e adopt the structure of a 1,3-diborataallene system, where lithium-diethyl ether units are bridging the twisted B-C-B axis from both sides. 

Lithium diethylamide has been shown to be an effective initiator for the homopolymerization of dienes and styrene llr2). It is also known that such a polymerization process is markedly affected by the presence of polar compounds, such as ethers and amines (2,3). However, there has been no report of the use of a lithium amide containing a built-in polar modifier as a diene polymerization initiator. This paper describes the preparation and use of such an initiator, lithium morpholinide. A comparison between polymerization with this initiator and lithium diethyl amide, with and without polar modifiers, is included. Furthermore, we have examined the effects of lithium-nitrogen initiators on the copolymerization of butadiene and styrene. 

Lefebvre and Evans found that lithium diethyl phosphite [(EtO)2POLi] adds to (Ss)-N-benzylidene-p-toIuenesulfinamide (126) to give (Ss,S)-128 in 85% yield and 84% de.77 The diastereomeric excess was improved to 93% de by using the sodium salt and to >97% with lithium diisopropyl phosphite. Transition state 127, involving si-face attack of the nucleophile, was proposed to account for the favored formation of 128. a-Aminobenzyl phosphonic acid 129 was obtained on hydrolysis of 128.78 Similar results were reported for the addition of diamido phosphite to 126.78... 

Crandall has shown that epoxide 195 is isomerized with ethereal lithium diethyl-arr ide chiefly to the allylic alcohol (76 %) and claimed that carbenic insertion products are absent.279 ... 

Fumarsaure 2-Lithium- -diethyl-ester E19d, 187 (H > Li) Maleinsiiure 2-Lithium- -diethyl-ester E19d, 187 (H - Li)... 

Enantiomerically pure substituted cyclohexanones, such as 9, react with lithium diethyl phosphite to give 5-(diethoxyphosphinyl)cyclohexanones 10 with complete diastereoselectivity 10 . 

The Horner-Wadsworth-Emmons reagent 735 (Scheme 180) prepared through Michaelis-Becker reaction of 4-(chloromethyl)-l-tritylimidazole 734 with lithium diethyl phosphonate reacts with aldehydes or ketones to give 4-vinylimidazoles 736 <2002S1072>. 

Anhydrous samarium(III) chloride [Rare Earth Products, Johnson Matthey] (2.40 g, 9.40 mmol) is placed in a 200-mL Schlenk tube containing a magnetic stirring bar. Tetrahydrofuran (THF) (100 mL) is introduced via a cannula at 20 °C. The mixture is stirred at 20 °C for 2 h. Solid (2,6-di-tert-butylphenoxo)-lithium-diethyl etherate (8.13g, 28.4 mmol) is added to this slurry at 20 °C. A reflux condenser is then fitted to the Schlenk tube, and the reaction mixture is heated under reflux for 8 h. After h, the solid dissolves to yield a clear yellow-green solution. The solvent is removed at 25 °C and 10 torr, leaving a yellow-green solid, which is scraped from the sides of the Schlenk tube with a spatula and transferred to a sublimation tube. Sublimation at 255-260°C and 10 torr affords yellow crystals of tris(2,6-di-tert-butyl-phenoxo)samarium. Yield 4.46 g (62%). ... 

Dialkyl l-lithio-l,l-difluoromethylphosphonates are usually generated in situ at low temperature from difluoromethylphosphonates in the presence of LDA or LiHMDS. Because of tlieir instability (rapid dissociation to give difluorocarbene and lithium diethyl phosphite) and poor nucleophilicity, 152,462. these highly deactivated carbanions require very powerful electrophiles in order to obtain satisfactory results. 

Another variation of the classic Darzens reaction is a one-pot synthesis of dietliyl 1-perfluoro-alkyl-1,2-epoxyalkylphosphonates using the nucleophilic attack of lithium diethyl phosphite on the carbonyl carbon of perfluorinated P-oxophosphonium salts (Scheme 4.8). The resulting intermediate can eliminate in two directions. When the oxygen anion in the least sterically hindered position (R = R = Me) attacks the neighboring carbon atom, diethyl 1-perfluoroalkyl-1,2-epoxyalkylphosphonates aie obtained in moderate yields (42-51%) after elimination of PhjP (anti fashion). The formation of a-(perfluoroalkyl)vinylphosphonates by attack at phosphorus (syn fashion) can be a competing reaction. The results indicate that the selectivity can be controlled to produce exclusively either epoxyphosphonates or vinylphosphonates. ... 

The preparation of diethyl 3,3-diethoxy-2-hydroxypropylphosphonate in 38% yield is possible through the addition of lithium diethyl phosphite to a mixture of D-glycidaldehyde diethyl acetal and BFgEtgO at -80°C in THF (Scheme 5.26)3 The relatively low yield may be explained by deactivation of the epoxide and the weakly nucleophilic character of the phosphite anion. Deprotection of the formyl group is accomplished under mild conditions with 0.1 M HCl at 40°C. ... 

Diethyl cyanomethylphosphonate anion undergoes halogenation, rendering it a convenient precursor of diethyl 1-cyano-l-fluoromethylphosphonate. Thus, treatment of an aqueous solution of sodium enolate of diethyl 1-cyano-1-formyhnethylphosphonate with fluorine gives diethyl 1-cyano-1-fluoromethylphosphonate in 61% yield after concomitant deformylation (Scheme 6.12)." "° In contrast, treatment of unprotected lithium diethyl cyanomethylphosphonate with (CF3SO2)2NF in THF at low temperature leads to 1-cyano-1-fluoromethylphosphonate in lower yield (51%). "... 

This sequential Michael and Homer-Wadsworth-Emmons reactions has been developed with a large variety of charged nucleophiles such as Uthium carbanions of phenylethynyl, methyl[(meth-ylsulfoxyl)methyl]sullide and ethyl a-(methylthio)acetate5 ° or lithium diethyl phosphite to prepare functionalized dienes, trienes, and their analogues. 

An efficient, versatile protocol for the synthesis of highly enantioenriched a-aminophosphonate has been devised. The addition of lithium diethyl phosphite in THF at room temperature to imines prepared from methyl and methoxymethyl (MOM) ethers of (7 )-(-)-2-phenylglycinol and a wide variety of aldehydes has been explored. The reaction generates predominantly the (R,R) diastereomers whose hydrogenolysis produces a-aminophosphonates in good yields (Scheme 8.67). 

Corey and Posner8 have prepared lithium di-n-butylcopper and lithium diethyl-copper and used them for cross coupling in the same way. In general they are more reactive but also less stable thermally. They also tend to induce halogen-copper exchange more than lithium dimethylcopper, but this side reaction can be reduced by addition to the reaction mixture of an excess of the alkyl halide corresponding to the n-alkylcopper reagent. Yields of 60-80% were obtained. 

---