Ether adduct

A solution of 2.5 g (45 mmol) of (Z)-2-butene, 40 mmol of butyllithium and 4.5 g (40 mmol) of /-BuOK in 30 mL of THF is kept for 15 h at — 50 °C. The solution is cooled to —75 C and 20 mL (88 mmol) of the 1 1 fluorodimethoxyboranc-dicthyl ether adduct are added, followed 1 h later by 44 mmol of benzaldc-hyde, The mixture is stirred at — 75 C for an additional hour and is then warmed to 25 C over 30 min and diluted with 100 mL of diethyl ether, washed with three 50-mL portions of NaCl and evaporated. The product is chromatographed on silica gel eluting with hexane/diethyl ether 4 1 and is further purified by distillation yield 40% d.r. (synjanti) 96 4. 

The first diazonium-salt-crown-ether adduct was isolated and identified as a 1 1 complex by Haymore et al. (1975). Unfortunately Haymore never published the X-ray structural analysis of benzenediazonium hexafluorophosphate with 18-crown-6 which he performed in 1980. ORTEP drawings with measured bond angles and lengths from Haymore s investigation can be found in a review chapter by Bartsch (1983, p. 893). A few data from Haymore s work (e.g., R = 0.064) were also mentioned by Cram and Doxsee (1986, footnote 7). Groth (1981) published the results of his X-ray investigation of 4-methoxybenzenediazonium tetrafluoroborate and 21-crown-7 (R = 0.042) and Xu et al. (1986) those of 4-methoxybenzenediazonium tetrafluoroborate and dibenzo-24-crown-8 (R = 0.086). 

Closely related to the crown ether adducts are the two intramolecular arenediazonium ion-crown ether compounds 11.6 and 11.7 which were synthesized by Gokel s group (Beadle et al., 1984b). Infrared and lH NMR spectra are consistent with the insertion of the diazonio group into the 21-crown-7 cavity. The complex 11.6 can therefore be described not in an anthropomorphic, but in a zoomorphic way, as an ostrich complex reflecting the common belief that an ostrich hides its head in a hole when endangered. For the complex 11.7 the spectra correspond to... 

The crown-ether adduct shown in Scheme 13 exhibits both inter- and intramolecular C—H O hydrogen bonding in the solid state (Figure 3)7 ... 

The displacement of one base coordinated to a stannylene SnX2 by another base can easily be achieved if the entering molecule is more basic than the leaving one. If an ether solution of 1 is allowed to react with pyridine, the weak ether adduct is converted to a pyridine adduct at —30 °C 112,134) ... 

The combination of equimolar amounts of tris(trimethylsilyl)methyllithium and zinc bromide in a THF/diethyl ether mixture, Scheme 27, furnished tris(trimethylsilyl)methylzinc bromide, as a lithium bromide/ether adduct.43 The compound, which may also be formulated as a lithium alkyldibromozincate, showed no ligand redistribution reactions. It is monomeric in solution and can be treated with 1 equiv. of an organolithium reagent to afford heteroleptic diorganozinc compounds. 

It is interesting to note that another reaction pathway is observed when the pyridine adduct of HBF4 is used as substrate instead of the ether adduct. In this case exclusively oxidative addition of HF takes place to give compound 15.32... 

The products are triazolines with the amino or alkoxy function in the 5-position Addition is regiospecific. In some cases the triazolines aromatize spontaneously more usually, aromatization is effected by heating the compounds alone (for enol ether adducts) or with acid or base. 

Sheradsky has found that the hydroxyl function of a ketoxime such as acetophenone oxime can be made to react with DMAD when the reaction is carried out in methanol with a basic catalyst, to give mixture of the fumarate and maleate isomers (164) in the ratio 2 1. This mixture on heating undergoes a hetero-Cope rearrangement followed by cyclization and dehydration to give dimethyl 5-phenylpyrrole-2,3-dicarboxylate (168) (Scheme 25). Similarly, Heindel and Chun have reported that vinyl ether adducts (171), obtained by the condensation of arylamide oximes with DMAD, get thermally converted into oxa-diazolines (172) or imidazolinones (174), depending on the reaction conditions. A similar reaction occurs with aromatic amidoxime-methyl propiolate adducts to give imidazoles (170) (Scheme 26). 1,2,4-Dioxazoles have been reported to be formed in the reaction of hydrox-amic acids with DMAD. - ... 

The simplest reaction is addition of a proton (usually from a strong non-coordinating acid, such as HBF4, HPFg, HOTf often as their ether adducts) to give the corresponding carbyne (Equation 1.20) ... 

Generally, during the first step, a diethyl ether adduct of the alane is synthesized, which should not be isolated and can be used for the next step (Eq. 2) in situ . This method to generate the alane has the advantage with respect to other procedures to start from the easily available lithium alanate (which should be purified before use). The reaction with the alcohol or silanol can be followed by the evolution of gaseous hydrogen. Depending on the acidity of the alcohol or the silanol the reaction mixture has to be cooled. 

Acid-Catalysed Conversion of Vinyl Ethyl Ether Adducts into Alcohols... 

Concentrated aqueous HC1 (36%) (0.5 ml) is added to a mixture of 0.10 mol of the vinyl ether adduct and 50 ml of methanol. The mixture is heated for -15 min in a bath at 50 C, then the acetaldehyde acetal and the greater pan of the solvent is removed using a rotary evaporator (note 1). Water (-50 ml) is added, after which the product is extracted with Et20. The ethereal solution is washed with water, then dried over MgSC>4 or K2C03. The product is isolated in the usual manner. 

Blasius, E., Nilles, K.-H., The removal of cesium from medium-active waste solutions. 1. Evaluation of crown ethers and special crown-ether adducts in the solvent extraction of cesium, Radiochim Acta, 35,173-182,1984. 

Five membered heterocycles, containing more than 1 heteroatom were also used in Sonogashira reactions. 4-Iodopyrazole, protected in the form of its ethyl vinyl ether adduct (6.51.) was reacted with a series of acetylenes and the acidic workup of the crude product led to 4-ethynylpyrazole derivatives in good yield.77... 

The calcium silylamide Ca N(SiMe3)2 2, or its ether adducts, has been used as a synthon to generate numerous other related derivatives. These include phosphanides, arsa-nides," thiolates, " selenolates and tellurolates, as well as a variety of diaza-substimted complexes, some of which were discussed above (see also Ref. 11). 

The isomerization of allyl ethers to 1-propenyl ethers, which is usually performed with potassium tert-butoxide in dimethyl sulfoxide, can also be carried out under milder conditions using tris(triphen-ylphosphine)rhodium chloride,208 and by an ene reaction with diethyl azodicarboxylate,209,210 which affords a vinyl ether adduct. Removal of an O-allyl group may be achieved by oxidation with selenium dioxide in acetic acid,211 and by treatment with N-bromosuccinimide, followed by an aqueous base.201,212... 

MF5 reacts with aliphatic ethers to yield volatile adducts of the [MF5(OR2)] type DMSO forms the bis adducts [MF5(DMSO)2]. MCI5 and MBr5 form numerous [MX5(ether)] adducts. Abstraction of oxygen from the ethers occurs at around 100 °C to produce oxo trihalides and alkyl halides.1 The ability of crown ethers to coordinate and reduce MC1S has been explored 104 [(MC15)2L] and [MC1SL] were isolated with L = dibenzo-18-crown-16, 18-crown-6 and 15-crown-5. NMR data indicate that these compounds disproportionate. 

IV,N,N -Tris(trimethylsilyl)amidines have been used recently as precursors for a number of inorganic heterocycles and metallacycles,1 some of which are being studied in light of their unusual solid state properties2. Boere et al. reported the synthesis of several aryl-substituted persilylated benzamidines and the related compound /V,N,N, N",N",Ar" -hexakis(trimethylsilyl)-l,4-benezenedicarboximidamide (hereafter referred to as HBDA) 3 the present syntheses, which are generally based on the same reaction of an aryl-substituted carbonitrile with lithium bis(trimethylsilyl)amide, offer more facile routes to representative mono- and polyfunctional carboximidamides (i.e., amidines) as well as the prototypal derivative N,N,N -tris(trimethyl-silyl)formimidamide.4 As before, the crystalline diethyl ether adduct of lithium bis(trimethylsilyl)amide5 is favored over the nonsolvated amide in these syntheses the preparation of the diethyl ether adduct is also described here. 

Mikami has also reported a related ene-like process involving glyoxylates and ketone-derived enolsilanes 42 (Eq. 8B2.11) [17]. The enol ether adducts 43 yield the corresponding P-hydroxy ketone upon treatment with mild acid. On the basis of an analysis of the stereo- and regiochemical outcome of the addition reaction Mikami has invoked a monodentate complex between aldehyde and metal, in contrast to the typical transition-state structures involving glyoxylates that are suggested to involve metal/aldehyde chelates. 

The method has been extended by the use of reactive intermediate oxonium ions such as sulfonyl cation-ether adducts, dialkyloxycarbenium salts with ether, and so on. The more reactive dialkyl halonium ions also readily alkylate dialkyl ethers to the corresponding oxonium ions."... 

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