Halogenides

Extensive gas-phase structural studies have been performed on fluoro-substituted cyclopropanes. Important structural parameters are collected in Table 9. 

TABLE 9. Bond lengths (A) and bond angles (deg) in halogen-substituted cyclopropanes  

Ring geometry and substituent positions change analogously in oxirane upon fluorine substitution (see References 160,163,174 and references cited therein). 

Up-to-date gas-phase data are available only for a few purely chloro- or bromo-substi-tuted cyclopropanes (Table 9). The distal bond is lengthened in 107 and 110, but no ring asymmetry was detected in 106. The mean C—C length is close to that in 1. Two possible models of 110 have been obtained from a joint analysis of ED and MW data and ab initio calculations171, but unfortunately, neither of them reproduces the A0 rotational constants from the earlier and from a more recent MW study17. 

The cis Cl Cl contact decreases further to 3.22 A in 109, accompanied by a closing of the C—C—Cl angles and a lengthening of the ring C—C bonds170 (Table 9). Steric effects play similarly an important role in the structures of 111 and 112172. Mean intramolecular cis Br Br distances are 3.50 A172 and 3.40 A (calculated from the original data), respec- 

A fluorine substituent shortens the adjacent C—C bonds and lengthens the opposite bond in the cyclopropane ring. The lengthening of the C—C bond opposite to a CF2 group is remarkable (cf 98 and 104 in Table 9), but the mean C—C distance is smaller even in these molecules than in cyclopropane (1). In the other fluoro derivatives, all C—C bonds are shorter than in 1. The C—C bonds appear to be longer, the C—F bonds shorter in a cis isomer than in the trans isomer , and the same applies to C—C and C—F bonds in cis compared to trans CHF—CHF moieties within the same molecule. Ab initio calculations with a 4-2IG split valence basis set reflect the above trends quite well, except for the distinction of effects in the cis and trans forms . The additivity of substituent effects, which 

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Acid Halogenides. For acid halogenides the name is formed from the corresponding acid radical if this has a special name (Sec. 3.1.2.10) for example, NOCl, nitrosyl chloride. In other cases these compounds are named as halogenide oxides with the ligands listed alphabetically for example, BiClO, bismuth chloride oxide VCI2O, vanadium(lV) dichloride oxide. 

Treatment of 8-[(4-cyanophenyl)methoxy]-7-formyl-2-cyclopentyl-2,3,4,6,11,1 la-hexahydro-l//-pyrazino[l,2-i]isoquinoline-l,4-dione with (Et0)2P(0)CH2C00Et and NaH in THF at 40 °C overnight, or with (2-pyridylmethyl)-, 4-[(ethoxycarbonyl)benzyl]-, (4-nitrobenzyl)-, and (meth-oxymethyl)triphenylphosphonium halogenide in the presence of KH in THF at room temperature gave 7-ethylene derivatives 386 (98MIP7). 

Alkali-gehalt, m. alkali content. gelb, n. alkali yellow. -gestein, n. alkali rock, -halogenid, n. alkali halide, alkalihaltig, a. containing alkali. 

To a solution of 5 mmol of 1,3-diphcnyl 3-[(S )-2-mcthoxymethyl-l-pyrrolidinyl]-2-propenyl[lithium in 10 mL of tort-butyl methyl ether (prepared according to Section D. 1.1.1.2.2.3.) at 0°C. 6.25 mmol of the aldehyde (and eventually 6.25 mmol of lithium halogenide in 27 mL of leri-butyl methyl ether) are added dropwise. Stirring is continued for 2 h and 0.39 g (5.0 mmol) of acetyl chloride are added. After 2 h stirring at r.t., 10 mL of the solvent, 50 mL of diethyl ether and 10 mL of 2 N aq hydrochloric acid are added and stirring is continued for 2 h at 20 C. The organic layer is extracted with three 20 mL-portions of water and the aqueous solutions are reextracted with diethyl ether. The combined aqueous solutions are dried over Na,S04, concentrated in vacuum and the residue distilled to yield a mixture of xyn- and on/i-ketones >90% ee, determined by H-NMR with Pr(hfc)3. 

The formation of high polymers of olefins in the presence of titanium halogenides with no specially added organometallic co-catalysts was discovered long ago [see (147), and the references therein], A complete description of various alkyl-free polymerization catalysts based on the use of transition metal chlorides may be found in the review by Boor (17), where a comparison of these catalysts with traditional two-component systems is given. 

In most cases one-component catalysts based on halogenides of transition metals were obtained with the help of various specific activation pro-... 

The activation by various nonorganometallic additives (149, 152-155) (metals, alkylhalogenides, diazocompounds, halogenides of transition and base metals, donor-type compounds). 

Olefin polymerization by catalysts based on transition metal halogenides is usually designated as coordinated anionic, after Natta (194). It is believed that the active metal-carbon bond in Ziegler-Natta catalysts is polarized following the type M+ - C. The polarization of the active metal-carbon bond should influence the route of its decomposition by some compounds ( polar-type inhibitors), e.g. by alcohols. When studying polymerization by Ziegler-Natta catalysts tritiated alcohols were used in many works to determine the number of metal-polymer bonds. However, as it was noted above (see Section IV), in two-component systems the polarization of the active bond cannot be judged by the results of the treatment of the system by alcohol, as the radioactivity of the polymer thus obtained results mainly from the decomposition of the aluminum-polymer bonds. 

This reaction also takes place with halogenides of dibasic acids. Thus adipoyl chloride and diethyl phosphite are reacted at 90°C for 8 h yielding adipyl-diphosphonic acid diethyl ester, according to Eq. (41). 

Selective reaction of the complex-bounded A1C13 with alkali halogenides. 

Natrinm-flnoro-tiihydrido-borat reduziert Vinyl-halogenide selektiv zu Olefinen (S. 400). Es wird aus Di-boran und Natriumfluorid hergestellt. 

Carbonsaure-halogenide > Aldehyde > Ketone > Carbonsaureester > Nitrile > Carbonsauren > Oxirane > Olefine... 

Carbonsauren > Olefine > Aldehyde > Ketone > Nitrile 80xirane > Carbonsaureester > Carbonsaure-halogenide... 

Die komplexen Borhydride mit echt salzartiger Struktur (z.B. Kalium-, Natrium-bora-nat) haben ein geringeres Reduktionsvermogen und reduzieren von obigen Gruppen meist nur Carbonsaure-halogenide und in gewissen Fallen Carbonsaureester, wahrend die komplexen Aluminiumhydride (z.B. Lithiumalanat, Natrium-bis-[2-methoxy-athoxy]-hydri-do-aluminat) auch Carbonsaure-Salze reduzieren. 

Carbonsaure-halogenide werden durch fast alle Metallhydride bzw. komplexen Hydride zu Aldehyden bzw. Alkoholen reduziert. Mit Trialkylzinn- und -silicium-hydriden werden Carbonsaure ester erhalten. Als Losungsmitteldienenmeist Ather, bzw. es wird ohne Losungsmittel gearbeitet. Die Reaktion verlauft mit nucleophilen Hydriden schnel-ler. 

Tab. 16 gibt einen Oberblick iiber die Moglichkeiten der Carbonsaure-halogenid-Reduktion. 

Komplexe Metallhydride reduzieren Carbonsaure-halogenide zu Alkoholen5,6 ... 

Halogen-carbonsaure-halogenide werden i. a. durch das elektrophile Lithiumala-nat/Aluminiumchlorid mit besseren Ausbeuten reduziert als mit Lithiumalanat, zudem hangen die Ausbeuten nicht von der Zugabemethode ab4 5. 

Auch Briickenkopf-Halogen-Atome sowie Halogen-aromaten, Vinyl-halogenide usw. werden mit uberschiissigem Lithiumalanat bei geniigend hohen Reaktionstemperaturen zu Kohlenwasserstoffen reduziert4. 

Bei der Hydrogenolyse aromatischcr Halogenide 2 und bei der selektiven Reduktion alicyclischer geminaler Dihalogen-Verbindungen13 wird ein Vierzentren-Mechanismus angenommen. 

Benzyl- und Allyl-halogenide werden durch Lithiumalanat/Chrom(III)-, Vanadium(III)-, Titan(III)- und Wolfram(VI)-chlorid-Systeme zu substituicrten Athanen, geminate Dihalogenide zu substituierten Athylenen gekoppelt, vicinale Dibromide zu Alkenen debromiert8. 

Diphenylmethyl-halogenide konnen durch Natriumboranat in Sulfolan hydrogenolysiert werden. 

Sek. Alkyl- und Cycloalkyl-halogenide reagieren zunehmend schlechter in der Folge ... 

In Gegenwart von 5 Mol% Aluminiumchlorid lauft die Reduktion prim., sek. bzw. tert. Halogenide meistens auch unter Eiswasser-Kuhlung schnell und exotherm ab. Durch... 

Deuterolyse primarer Alkyl-halogenide wurde bewiesen, daB vor der Reduktion eine Um-lagerung zum stabileren Carbokation eintritt1. 

Die Reduktion kann auch durch Palladium/Aktivkohle katalysiert werden1. Trichlor-siliciumhydrid reduziert Halogenide bei Belichten nach einem radikalischen Mechanismus2. 

Vinyl-halogenide lassen sich in der Regel mit Organo-zinnhydriden nur schwierig dehalogenieren6,1. 

Prim. Propargyl-halogenide reagieren in den meisten Fallen uberwiegend nach dem SN2-Mechanismus, so da 3 als Hauptprodukt Acetylene erhalten werden z. B.4 ... 

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