Lithium deuteri

In certain cases this reduction (with lithium aluminum hydride) takes a different course, and olefins are formed. The effect is dependent on both the reagent concentration and the steric environment of the hydrazone. Dilute reagent and hindered hydrazone favor olefins borohydride gives the saturated hydrocarbon. The hydrogen picked up in olefin formation comes from solvent, and in full reduction one comes from hydride and the other from solvent. This was shown by deuteriation experiments with the hydrazone (150) ... 

Both diastereoisomers of -homothreonine derivatives (109) and their 2-deuteriated analogues have been synthesized by 1,4-addition of homochiral lithium amides (107) as nitrogen nucleophiles to y-alkoxyenoates (108) (Scheme 13). The product distribution of the 1,4-addition depends strongly on the nature of the substrate (110) vs... 

As for LiC2H2, the authors have shown spectroscopically by using partial asymmetrical deuteriation [Li (CH2CD2)m] that lithium bridged symmetrically the carbon-carbon bond . Possible structures for the Li(C2H4) , n = 1, 2, and 3 complexes are depicted in Scheme 4. 

The treatment of the deuteriated cis oxirane 32 by EDA in HMPA yields exclusively the nondeuteriated alcohol 33. Indeed, complexation of the lithium cation by HMPA prevents the formation of the six-center transition state. The isomerization thus follows a more common E2 process, i.e. anti -elimination. 

One of the syntheses of f1udalanine begins with base promoted condensation of ethyl fluoroacetate and ethyl oxalate to give This is then converted by hydrolytic processes to the insoluble hydrated lithium salt of fluoropyruvate (58). This last is reductively aminated by reduction with sodium boro-deuteri de and the resulting racemate is resolved to give D-flu-dalanine (59). 

The deuteriated (97%) imines 363 and 365, and the hydrazone 364 have been prepared396-399 by treating 2,6,6-trideuterio-2-methylcyclohexanone and 2,2,6,6-tetradeuteriocyclohexanone with the corresponding deuteriated ammonium salts (RND3CI) and used in the KIE studies of the metalation of the above C=N compounds with lithium diisopropylamide (LDA) in THF, in N, N, N A -tetramethyl ethylenediamine (TMEDA) and in dimethylethylamine (DMEA) solvents (equation 200). The rates, d[imine]/dt of that of imines 363 and 364 metalation are zero order with respect to [THF], [TMEDA]... 

SCHEME 68. Influence of the experimental conditions on the deuteriation of 3-methyltetralone lithium enolate333 334... 

Besides its use as a mechanistic probe, deuteriation of anions under kinetically controlled conditions is a potentially promising way to access deuteriated molecules in a regio- and stereo- controlled manner, in opposition to the thermodynamic equilibration in the presence of an excess of deuterium donor. Thus, treatment of the lithium anion of 2-methyltetralone (p E = 7.31, pfsfEa = 10.8, pKkr = 18.1 in water)335, by one equivalent of a solution of deuterium chloride in deuterium oxide, generates the intermediate O-deuteriated enol whose reaction with water or with an excess of deuterium chloride in deuterium oxide conducts to, respectively, the tetralone or the deuteriated tetralone (Scheme 69)336. 

A careful study of the C-deuteriation of a series of preformed endocyclic337 and acyclic or exocyclic lithium enolates has recently been carried out by Eames and coworkers338, extending their previous observations on protonation339. 

SCHEME 69. Effect of the acidity on the protonation and deuteriation of the 2,4-dimethyltetralone lithium enolate336... 

Yur ev et al. 2 prepared deuteriated selenophenes from the respective halogenated compounds by halogen-deuterium replacement. Thus, 2-deuterio-, 2,5-dideuterio-, tetradeuterioselenophene, 3-methyl-, and 5-methyl-2-deuterioselenophene were obtained from the corresponding iodoselenophenes on reduction by zinc in deuteriated acetic acid. 3-Deuterioselenophene was obtained from 3-selenienyl-lithium hydrolyzed with deuteriated acetic acid at — 7 0°C the lithium derivative was obtained from 3-bromoselenophene and ethyllithium, also at — 70°C. The deuterium content was determined by combustion, the water being analyzed by the drop method.43... 

Dihenzylketoxime refluxed 2-5 hrs. with excess LiAlH4 in tetrahydrofuran ci5-2-phenyl-3-benzylaziridine. Y 73%. F. e., also deuteriated aziridines with lithium aluminum deuteride, s. K. Kitahonoki et al., Tetrah. Let. 1965, 1059. 

Amines.— The deuteriated ammonium iodide (341) is converted into its ylide irreversibly by n-butyl-lithium in pentane, but reversibly by potassium amide in liquid ammonia. Hence cis- and truns-cyclo-octene were obtained in a ratio of 70 30, respectively, together with labelled iViV-dimethylbutylamine when (341) was treated with n-butyl-lithium in pentane, and in a ratio of 32 68, respectively, together with unlabelled NN-dimethylbutylamine when (341) was treated with potassium amide in liquid ammonia. Sodium in liquid ammonia reduction of the oxime of 3,4-benzocyclohept-3-enone gives 4-amino-1,2-benzocycloheptene, which has interesting pharmacological properties. 

Properties and Reactions. There have been interesting further developments in the synthetic utility of 1,3-dithians. Deuteriation or methylation of the lithium salts of conformationally fixed 1,3-dithian derivatives occurred with high stereospecificity to give the deuterio or methyl derivative equatorially orientated at C(2). For example, cw-4,6-dimethyl-l,3-dithian... 

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