Dichloromethane, reaction

Enantioselectivities were found to change sharply depending upon the reaction conditions including catalyst structure, reaction temperature, solvent, and additives. Some representative examples of such selectivity dependence are listed in Scheme 7.42. The thiol adduct was formed with 79% ee (81% yield) when the reaction was catalyzed by the J ,J -DBFOX/Ph aqua nickel(II) complex at room temperature in dichloromethane. Reactions using either the anhydrous complex or the aqua complex with MS 4 A gave a racemic adduct, however, indicating that the aqua complex should be more favored than the anhydrous complex in thiol conjugate additions. Slow addition of thiophenol to the dichloromethane solution of 3-crotonoyl-2-oxazolidinone was ineffective for enantioselectivity. Enantioselectivity was dramatically lowered and reversed to -17% ee in the reaction at -78 °C. A similar tendency was observed in the reactions in diethyl ether and THF. For example, a satisfactory enantioselectivity (80% ee) was observed in the reaction in THF at room temperature, while the selectivity almost disappeared (7% ee) at 0°C. 

Chiral imines derived from 1-phenylethanone and (I. Sj-exo-l, 7,7-trimethyIbicyclo-[2.2.1]heptan-2-amine [(S)-isobornylamine], (.S>1-phenylethanamine or (R)-l-(1-naphthyl) ethanamine are transformed into the corresponding (vinylamino)dichloroboranes (e.g., 3) by treatment with trichloroborane and triethylamine in dichloromethane. Reaction of the chiral boron azaenolates with aromatic aldehydes at 25 "C, and subsequent acidic hydrolysis, furnishes aldol adducts with enantiomeric excesses in the range of 2.5 to 47.7%. Significantly lower asymmetric inductions are obtained from additions of the corresponding lithium and magnesium azaenolates. Best results arc achieved using (.S )-isobornylamine as the chiral auxiliary 3. 

Two AIBN-type radical polymerization initiators have been synthesized starting from commercial 4,4 -azo-bis(4-cyano)valeric acid (1) (Scheme 1) ACTP 3 -trichlorosilylpropyl-4,4 -azo-bis(4-cyano)valerate (4a) and ACTU 11 "-trichlorosilylundecyl-4,4 -azo-bis(4-cyano) valerate (4b). After thorough drying of the wet diacid 1, it was transformed into its chloride (2) using an excess of phosphorus pentachloride in dichloromethane. Reaction of 2 with the unsaturated alcohols allyl alcohol and 10-undecen-l-ol respectively gave the esters 3 in high yields which in turn led to ACTP (4a) and ACTU (4b) on Pt-catalyzed hydrosilylation. 

The reaction of 1,2-diaininocyclopropenylium perchlorates 14 with an equimolar amount of mercury(ll) acetate in dimethyl sulfoxide at 120 C afforded the cationic mercury complexes 15 as colorless crystals. The original cation salts 14 were recovered quantitatively when the complexes 15 were heated with perchloric acid in ethanol.Complexes 15 were also converted into l,2-diamino-3-iodocyclopropenylium ions 16 in 55% yield when treated with two molar equivalents of iodine in dichloromethane. Reaction of complexes 15 with sulfur in pyridine afforded the 2,3-diaminocyclopropenethiones 17 in 35% yield. 

Checkers obtained yields about 30% lower than reported probably because of incomplete precipitation of the products from the dichloromethane reaction solution. After the addition of the arene, the reaction of MnfCOisBr with AgBF4 was monitored by IR spectroscopy. In some reactions, it was found that additional AgBF4 (up to 20%) was required to completely convert all Mn(CO)5Br. 

In the simple benzenoid compound 3,4-dimethoxybenzoylcyanide in ether, benzene, toluene or dichloromethane, reaction with phenylhydroxylamine occurred at ambient temperature to give O-(3,4-dimethoxybenzoy0-N-phenylhydroxylamine in 90% yield accompanied by HCN evolution (ref.87). 

Gurjar and co-workers prepared several novel carbohydrate-based spirocycles and a spirocyclic proline derivative for applications in peptide, nucleoside, and carbohydrate synthesis. Ring-closing metathesis of carbohydrate diene precursor 78 furnished the corresponding spirocycle 80 in 88% yield using a catalytic amount of 3 in dichloromethane. Reaction of proline derivative 79 under similar conditions gave the corresponding spirocyclic peptide 81 in 96% yield. 

Figure 5.8 (a) ESI mass spectrum in the positive ion mode of the reacting solution of trans-anethole (2) (0.5 mmol L ) and tris p-bromophenyl)aminium hexachloroantimonate (1) (5.0mmol L" ) in dichloromethane (reaction time approx. 7 seconds), (b) ESI-MS/MS of the ion of m/z 148 of the same reacting solution... 

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