2-methyl-2-propane-, lithium

Nitronat Lithium-3-dimethylamino-carbonyl-2-methyl-propan- E19d, 1078 (En-olat -I- En —N02)... 

The use of hydrazone or enamine derivatives of ketones or aldehydes offers the advantage of stcreocontrol via chelated azaenolates. Extremely useful synthetic methodology, with consistently high anti selectivity, has been developed using azaenolates based on (S)- or (R)-l-amino-2-(methoxymethyl)pyrrolidine (SAMP or RAMP)51 58 (Enders method, see Section 1.5.2.4.2.2.3.). An example which illustrates the efficiency of this type of Michael addition is the addition of the lithium azaenolate of (5 )-l-amino-2-(methoxymethyl)pyrrolidine (SAMP) hydrazone of propanal (R = II) to methyl (E )-2-butenoate to give the nub-isomer (an 1 adduct) in 80% yield with a diastereomeric ratio > 98 2,... 

The addition of the lithium azaenolate of the SAMP hydrazone of propanal to methyl (E)-2-butenoate to furnish the (S,S,S)-adduct in 58% yield with > 96% ee and de is illustrative for the efficiency of this asymmetric Michael addition10°. Only the anti-isomer (an / adduct) is found. This methodology was used in the synthesis of pheromones of the small forest and red wood ant200. 

A cation arriving with a nncleophilic anion is another important factor. The nucleophile can attack the substrate in the form of a free ion or an ionic pair. As a rule, lithium salts are less reactive than sodium and potassium salts. Russell and Mndryk (1982) reported several examples of this. The sodium salt of ethyl acetylacetate reacts with 2-nitro-2-chloropropane in DMF yielding ethyl 2-(wo-propylidene) acetylacetate. Under the same conditions, the lithium salt does not react at all. Potassium diethyl phosphite interacts with l-methyl-l-nitro-l-(4-toluylsulfonyl)propane in THF and gives diethyl 1-methyl-l-nitro-l-phosphite. The lithinm salt of the same reactant does not react with the same substrate in the same solvent. 

Similarly, lithium aluminum hydride gives different products. / -Naphthyl p-toluenesulfonate affords p-thiocresol and ) -naphthol, and phenyl meth-anesulfonate gives methyl mercaptan and phenol. On the other hand, propyl p-toluenesulfonate yields />-toluenesulfonic acid and propane, and cetyl meth-anesulfonate and cetyl p-toluenesulfonate give hexadecane in 92% and 96% yields, respectively [680]. 

Lithium-2-propan-nitronat reagiert mit 4-(l-Azido-l-methyl-ethyl)-l-nitro-benzol in Ge-genwart von Phosphorsaure-bis-[dimethylamid] zu 4-Nitro-l-(2-nitro-l,1,2-trimethyl-pro-pyl)-benzol (92 %)2 l0. 

Lithium-1-alkine reagieren mit verschiedenen Nitro-alkanen bzw. mit Chlor-nitro-alka-nen in THF zu 3-Nitro-l -alkinen, z. B. reagiert 1-Lithium-propin mit 2-Chlor-2-nitro-propan zu 4-Methyl-4-nitro-2-pentin (20%)2 ... 

A stopper is lifted from the reaction flask while 500 mL of toluene are added to cover the solid residues. Propan-2-ol is added gradually to destroy any remaining organometallic compounds (excess Grignard or methyl-lithium). When this is complete (no further effervescence), water is added cautiously, followed by dilute hydrochloric acid to complete the solvolysis of the magnesium salts. 

Lithium-halogen exchange provides a versatile and often more facile alternative to lithium-hydrogen exchange. In particular, 1-bromocyclopropenes such as (77, R = Me) react very readily with lithium alkyls at 0 °C and below. The bromocyclo-propene may in principle be obtained by dehydrobromination of a dibromocyclo-propane, but an attractive alternative is the reaction of a trihalocyelopropane with two equivalents of methyl lithium, followed by trapping with an electrophile 39) ... 

Nitronat Lithium-2-(3,4-methylen-dioxy-phenyl)-3,3,3-tris-[methyl-thio]-propan- E19d, 1080 (En-olat + En —N02)... 

The impure lactone of 1-hydrozyoyoIohexaneaoetio acid and that of 2,2-dim thyl-8-phenyl hydracirylio acid react in the same way to give l-hydrozycydohexane-ethanol and 2-methyl-l-phenyl-1,2-propane-dlol respectively. The lactone of 2,2-diphenylhydracrylic acid, which ie crowded, does not react with metbylmagnesium iodide, but is reduced by lithium aluminum hydride to 2,2-diphenyl-1,3-propanediol with a yidd of S4%. 

Vinylaminyloxides 48 could be obtained by treatment of 2-methyl-2-nitroso-propane with lithium vinyl compound 476S In contrast to the intermediate vinyl-aminyloxide 40, 48 is prevented from secondary reactions apparently by the small spin density at the /5-carbon atom, which is caused by the strong twisting of the N-C bond. 

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