Bis-methanol adducts

Similar to their spontaneous 1,4-hydration in water, heterocycles 49a, 50a-e, and 50g all react simply upon dissolution in warm methanol to form his-addition products. The X-ray crystal structure of the bis-methanol adduct (51) derived from the diazaborine 50b clearly showed it to be a zwitterion comprised of tetrahedral borate anion and formamidinium cation fragments. Once again, 50f proved to be the only exception A weakly chelated dimethylborate ester (not shown) was found to be its structure in MeOH by B NMR. 

A preferable, three-step, procedure for preparing anhydrous bis(2,4-pentanedionato)zinc, m.p. 127°, in good yields involves (1) the preparation of bis(2,4-pentanedionato)zinc hydrate from zinc sulfate heptahydrate and 2,4-pentanedione in aqueous solution in the absence of heat, (2) conversion of the bis(2,4-pentanedionato)zinc hydrate into a bis (2,4-pentanedionato) zinc-methanol adduct, and (3) decomposition of the methanol adduct. 

The product crystallizing out of cooled methanol solutions appears to be an unstable methanol adduct of bis(2,4-pentanedionato)zinc. Recrystallization from hot alcohol yields the hydrate. Immediately after collection, this adduct melts at 80 to 90° on standing in the open atmosphere, it is converted into the hydrate. 

Ethynyl Terminated Monomer/Oligomer Mixtures from VI (VII). A mixture of the bis-butynol adduct, VI (3.9 mmol), toluene (40mL) and 10% methanolic K0H (40mL) was heated to reflux under nitrogen. The methanol and toluene were removed by distillation, adding more toluene as needed to maintain the reaction volume at 40mL. After... 

As expected, additions to alkynes are also subject to control by polar functions nearby. Thus, nucleophilic attack on trifluoromethylacetylene [116], cyanoacetylene [137], and ethylthioacetylene [138] occurs at the terminal jp-hybridized carbon atom, the substituent at the other end of the triple being an acceptor in all cases. This behavior is to be contrasted with the mode of addition on ethoxyacetylene [3 39], aminoacetylenes [120], The vinylogue, 4-dimethyl-aminobut-3-en-l-yne [121], reacts with aniline at the internal position of the akyne linkage. However, a 2 1 regiose-lectivity, favoring the methanol adduct predicted by the polarity alternation rule, has been observed for the addition of jV,jV-bis(trifluoromethyl)ethynylamine [122], It is not known whether steric factors play a role in the decreased regioselectivity. 

Tetraalkyldisilene 63 with a lattice framework in <7/-form dissociates into the corresponding silylene 128 [Eq. (50)],92 The treatment of (4S, 6S, 4/S, 6 S )-63 (dl-63) with methanol for 6 days at rt affords a racemic mixture of methanol adducts of silylene 128. Silylene 128 is also trapped by bis(trimethylsilyl)acetylene. 

Addition of lithium bis(trimethylsilyl)amide to perfhiorinated ketones and solvolysis of the N-Si bond in methanol resulted the formation of stable, isolable N-H imine Z-E isomer mixtures along with a methanol adduct. Enantioselective reduction of these three-component mixtures with oxazaborolidine catalysts and catecholborane provided trifluoromethylated amines in 72-95% yields and 75-98% ee 267... 

A mixture of reactive intermediates, including l,l-dimethyl-3,3-bis(trimethylsilyl)-Tsilaallene and dimethylsilylene, along with l,l-dimethyl-2,3-bis(trimethylsilyl)-l-silacyclopropene 86 were formed and detected from the direct irradiation of [(trimethylsilyl)ethynyl]pentamethyldisilane in hydrocarbon solution (Equation 21). These species were detected and identified using laser flash photolysis. They were trapped as their methanol adducts in steady-state irradiation experiments. Steady-state irradiation in the presence of methanol affords MeOH-addition products which are consistent with the formation of the silaallene, silacyclopropene, and silylene along with bis(trimethylsilyl) acetylene as the major product <1997JA466>. 

Complex 446 is a doubly chloro-bridged dimer in the solid state but is essentially monomeric in dichloromethane (or chloroform) solution (Scheme 101). Thus, coordination of an additional Lewis-basic solvent (S) molecule such as acetone, THF, and acetonitrile is feasible in a position tram to the Cp ligand to form a solvate, but no such stable solvates could be isolated. Methanol or water (X) displaces the ether side chain to form the bis(solvate) adducts however, the chelate is re-formed on removal of the solvent under vacuum to give stable methanol or water monoadducts. The THF-solvate of the water adduct has been structurally characterized. 

Silver nitrate-catalysed rearrangements in methanol of dibromocyclopropyl propellanes have been examined. For example, (80 R = Br) gave a mixture of the corresponding methyl ketal (80 R = OMe) and bicyclo[5,4,0]undec-l(7)-en-2-one, together with minor products. One step in a reported synthesis of 1,7-methano-[12]annulene involved addition of dibromocarbene to tricyclo[4,4,l,0 ]undeca-3,8-diene (81) followed by silver acetate-catalysed ring-opening of the resultant bis-dibromocarbene adduct to give a mixture of isomeric acetates. ... 

The 4-borauracils 129a,b were prepared by condensing a P-boronic amino acid with isocyanic acid or methyl isocyanate followed by Hoffinan elimination (Scheme 45) (2010MI33). The NMR spectrum indicated that the corresponding bis-methoxy adducts form when these compounds are treated with a large excess of methanol. 

Reaction of the bis-dibromocarbene adducts of cis,cis-cyclo-octa-1,5-diene with silver perchlorate in methanol gives (140 R = Me) and (141), together with (142) the monocyclic products are characterized by their n.m.r. spectra. ... 

Perfluorotetramethylthiadiphosphanorbornadiene and bis(trifluoromethyl) thiadiphosphole can be prepared by thermolysis of an adduct of methanol and hexakis(trifluoromethyl)-l,4-diphosphabarrelene with sulfur [113] (equation 23) Pyrolysis of the adduct of hexafluorinated Dewar benzene and phenyl azide results in ring expansion giving azepine, which photochemically yields an intramolecular 2-1-2 adduct, a good dienophile for the Diels-Alder reaction [114, //5] (equation 24) Thermolysis of fluonnated derivatives of 1,5-diazabicyclo-... 

Similar results were obtained in methanol (ref. 30), where for the bis-(trifluoromethyl) derivative the ratio between the return of the trans bromonium ion to the trans olefin and its collapse to products 2 and 6 is 4.5 and is again very strongly reduced by the presence of LiC104 (Table 9). In this solvent, however, return was not observed for unsubstituted stilbene, either. It can be observed that both cis - and trans -stilbene gave methoxybromo adducts in an anti stereospecific way, suggesting a nucleophilic assistance by the solvent. 

The bromination of /razw-stilbenes in methanol, trifluoroethanol and in acetic acid leads almost exclusively to the erythro adducts via a 100% anti addition, regardless the substituents and the solvent. In contrast, the stereochemistry of the reaction of c/s-stilbenes exhibits a considerable dependence on the substituents and on the solvents the reaction of p-methoxystilbenes is always stereo-convergent, that of p,p -bis(trifluoromethyl)stilbenes is stereo-specific in all investigated solvents, whereas unsubstituted stilbenes can produce variable stereochemical outcomes ranging from stereo-specific to stereo-convergent in going from methanol to trifluoroethanol as solvent. 

Cyclohexadienes are available by the methodology of Birch, and the reactions of l-methoxy-, 1,3-dimethoxy-, l,3-bis(trimethyl-silyloxy)-, and l-methoxy-4-methyl-l,3-cyclohexadiene with a number of 1,4-benzoquinones have been investigated. Acid treatment of the adducts and subsequent dehydrogenation provides a synthesis of 2-dibenzofuranols. Thus the adduct 159 (Scheme 41) from 1,4-benzoquinone and 1,3-dimethoxy-1,3-cyclohexadiene, on treatment with a trace of concentrated hydrochloric acid in ethanol at room temperature, affords the tetrahydrodibenzofuranone 161. When the adduct 159 is heated under reflux in aqueous methanol, the reaction can be arrested at the dihydrodibenzofuran 160. The tetrahydrodibenzofuranone 161 on dehydrogenation with palladized charcoal affords 2,7-dibenzofurandiol. ... 

Treatment of the 1 2 adduct 62 with one equiv. of hydrogen peroxide in methanol gave mainly a pure, crystalline compound (m.p. 209-210.5°) whose structure was presumed to be bis(3-0-acetyl-5,6-dideoxy -1,2-0 - isopropylidene - 6-C-nitro - / -L-idofuranose-5-yl)phenyl-phosphine oxide (69) therefore, the original 1 2 adduct 62 was assumed to be a mixture consisting mainly of the corresponding phosphine compound. 

However, in the presence of methanol the pyrandione (326) is the major product. This product is of course the cis isomer of the Michael adduct above and is considered to arise by isomerization of that species. The lower reaction temperature in the presence of solvent apparently favours isomerization at the expense of intramolecular cyclization (Scheme 94). A further product, formed in low yield in the absence of solvent, is the symmetrical bis-pyranone (327) which arises from a further Michael addition of the carbanion, this time at the sterically favoured 8-position of the enoate. 

The tetrakis complexes are easily obtained by the addition of an excess of the appropriate pyridine, in absolute ethanol or methanol, to a solution in the same solvent of the anhydrous nickel salt.147 The bis adducts are prepared by using stoichiometric amounts of the anhydrous reactants783 or by heating the corresponding tetrakis complexes at temperatures in the range 80-110 °C.784 820 Thermal decomposition of the bis and tetrakis adducts leads to the mono adducts. Using hydrated nickel salts as starting material may cause the formation of complexes with coordinated water molecules. 

Bis adducts of terpyridyl, [Ni(terpy)2]X2, can be obtained in ethanol solutions. The mono adducts can be obtained by thermal decomposition of the corresponding bis adducts or by the reaction of excess nickel salt with the ligand in water-methanol solutions. The [Ni(terpy)2]X2 complexes (X = Cl, Br) are six-coordinate863 whereas the mono adducts NiLX2 are five-coordinate when X = C1 or Br864,865 and polynuclear six-coordinate when X = NCS.866 In the last complex the nickel atoms are ferromagnetically coupled. 

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