Crystalline adducts

Peroxohydrates are crystalline adducts containing molecular hydrogen peroxide. These are commonly called perhydrates, but this name is better avoided because historically implied the maximum oxidation state and hjdrate implies the presence of water, neither of which apply to peroxohydrates. They have also been called hydroperoxidates (92). 

Complex Formation. B-Ttichlorobora2iQe was reported to readily form crystalline adducts of uncertain stmcture with pyridine (131). The Lewis acids aluminum tribromide or gallium trichloride form 1 1 adducts with hexamethylbota2iQe (eq. 36) ia which the metal atom coordinates with a nitrogen with loss of planarity of the ring (132,133). 

The intermediacy of dipolar species such as 186 has been demonstrated by reaction of enamines with 2-hydroxy-1-aldehydes of the aromatic series (129). The enamine (113) reacts in benzene solution at room temperature with 2-hydroxy-1-naphthaldehyde to give the crystalline adduct (188) in 91 % yield. Oxidation with chromium trioxide-pyridine of 188 gave 189 with p elimination of the morpholine moiety. Palladium on charcoal dehydrogenation of 189 gave the known 1,2-benzoxanthone (129). 

The reaction of enamines derived from cyclohexanone with dichlorocarbene to give the 1 1 adducts is now well established (137-139). The morpholine enamine (113) reacted with dichlorocarbene at —10 to —20° in tetrahydrofuran to give the stable crystalline adduct (201). Thermal decomposition followed by an aqueous work-up gave an a,)3-unsaturated ketone identified as 2-chloromethylene-cyclohexan-l-one (202) (139). 

Combination of stoichiometric amounts of H2S and SO2 at low temperature yields the white crystalline adduct H2S.SO3 which is isomeric with thiosulfuric acid. 

Trimethylphosphine and dimethylphenylphosphine form crystalline adducts (61) with chlorodiphenylphosphine. The adducts are in equilibrium with their starting materials in dichloromethane. 

The unequivocal proof is furnished by the crystal inclusion behavior of simple 2-hydroxy-3-naphthalenecarboxylic acid 25a46 , and its 1-chloro derivative 25b37 since both allow the formation of a crystalline adduct ( clathratocomplex 19)) with dimethylformamide with the expected 1 1 stoichiometric ratio37. Thus, the salicylic acid function (2-hydroxycarboxylic acid group) is shown to be an excellent sensor, or a good complementary site for the dimethylformamide molecule in solid state inclusion. 

Dimethyl- and diethylzinc reacted with dimethylpyrrole- and mesityl-substituted cyclopentadiene ligands to give monocyclopentadienyl(methyl)zinc and -ethyl(zinc) compounds. These products then formed, Scheme 20, crystalline adducts with tetramethylethylenediamine (TMEDA) such as 24, whose solid-state structure is shown in Figure 11. 

The actual value will be even more exothermic, since S b 1/ and S b 1, form stable crystalline adducts of type... 

The phosphadithiatriazenes form white crystalline adducts with norbomadiene which facilitate the characterization of the less stable R2PS2N3 compounds (R = Me, PhO) " . An X-ray structural determination of PhjPSjNj C Hg has confirmed the prediction, based on NMR spectroscopic data, that the cyclo-addition occurs in a l,3-S,S-fashion... 

Mechanochemically activated reactions between molecular solids to yield a co-crystalline adduct. 

If the crystals of 1 are exposed to bromine vapor, addition to the C=C double bond occurs without difficulty, as the molecules can anisotropically migrate along the cleavage plane and the quantitatively obtained trans adduct does not include large amounts of bromine. The gas-solid addition of 2 is more complicated. The initially formed crystalline adduct keeps large quantities of additional bromine and eliminates HBr upon standing and in solution by forming lactones. Thus, mixtures of products arise because consecutive reactions... 

Another classic anion reaction is that with bisulphite ion to yield crystalline adducts. The structure of these was long a matter of dispute before it was established that they were indeed salts of sulphonic acids (33), reflecting the greater nucleophilicity of sulphur rather than oxygen in the attacking anion. The effective nucleophile is almost certainly (34) rather than HSO3 (HO + HSO3 H O +... 

N-Phenylmaleimide is an active dienophile in the Diels-Alder reaction and usually gives crystalline adducts. 

The synthesis started with levoglucosenone 4, available by the pyrolysis of cellulose, e.g. old newspapers. Bromination-dehydrobromination gave the enantiomerically-pure Diels-Alder dienophile 5, which was combined with isoprene to give predominantly the crystalline adduct 1. Hydrolysis and acetylation led to 6, which was carried on to the geometrically-defined allylic alcohol 7 via reduction with Zn-Cu couple. Overman rearrangement of 7 proceeded with high facial control, to give 8. 

Diels-Alder additions provide one of the more extensively studied reactions of these heteroles, and many examples are listed in the reviews given at the beginning of this section. Typical additions often require heating, giving the 7-hetero-norbornenes and -norbor-nadienes as products of reaction with alkenes and alkynes (Scheme 209). The report that (131) resulted at room temperature from tolane and (120) was therefore surprising. Subsequent investigation showed it to be a 1 1 crystalline adduct from which tolane could be sublimed (Scheme 210) (72CC690). 

Diphenylfuro[3,4-6 ]quinoxaline (207) has been obtained (70TL1409) from the phthalide (206) as a green crystalline, quite stable solid (m.p. 244-246 °C). In DMSO (deep blue solution), (207) reacts instantaneously with such dienophiles as maleic anhydride, maleimide, dimethyl acetylenedicarboxylate and others to give crystalline adducts which, when heated to or above their melting points, decompose giving a blue color presumably due to reversal of the Diels-Alder reactions. 

The white crystalline adduct ZnCl2(btaH)2 (191) obtained by mixing the components in ethanol (172) or in aqueous HC1/NH3 solution (198) has been shown to possess the expected tetrahedral structure with N-3-coordinated benzotriazole ligands (198). The same components react together in 7 M ammonia solution to afford colorless, polymeric... 

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