Dichloromethylenation

Imtdazo[4,5-d]pyridaztne, l-benzyl-4,7-dtchloro-nucleophtlic displacement reactions, 5, 629 Imidazo[l,5-6]pyridazine-5,7(3H,6H)-dione, 4-acetyl-2-phenyl-synthesis, 5, 651 Imidazo[l, 2-6]pyridazines reactions, 5, 628 synthesis, 5, 650 Imidazo[ 1,5-6]pyridazines synthesis, 5, 651 Imidazo[4,5-c]pyridazines reactions, 5, 628-629 synthesis, 5, 651 Imidazo[4,5-d]pyridazines reactions, 5, 629 synthesis, 5, 436, 468, 651-652 3H-Imidazo[l,2-6]pyridazin-2-one, 6-chloro-3-dichloromethylene-synthesis, 3, 355... 

The nervous system is vulnerable to attack from several directions. Neurons do not divide, and, therefore, death of a neuron always causes a permanent loss of a cell. The brain has a high demand for oxy gen. Lack of oxygen (hypoxia) rapidly causes brain damage. This manifests itself both on neurons and oligodendroglial cells. Anoxic brain damage may result from acute carbon monoxide, cyanide, and hydrogen sulfide poisonings. Carbon monoxide may also be formed in situ in the metabolism of dichloromethylene. 

Phosphorane (dichloromethylene) TRIPHENYL 1, 46, 33 Phosphorous triamide, hexamethyl, 46, 42... 

RN 22560-50-5 MF CHzCljNaPsP MW 288.86 EINECS 245-078-9 CN (dichloromethylene)bis(phosphonic acid) disodium salt... 

G)H2Cl7N20 86567-35-0) see Apraclonidine (dichloromethylene)bisphosphonic acid tetrakis(l-methyl-ethyl) ester... 

A -Chloroalkylphosphazenes generally undergo preferential chlorine atom replacement at phosphorus with alcohols and amines. However, it has now been shown that the weakly basic arylsulphonamides may preferentially attack the a-dichloromethylene group ... 

Indirect confirmation of the structures of these products is provided by the fact that arylsulphonamides do not react with phosphazenes, R N=PCl3, where R does not contain an a-dichloromethylene group. During attempts to esterify chloroalkylbiphosphazenes, reaction took place at dichloro-methylene and phosphazene groups, but their relative reactivity was not determined... 

Dichloromethylene)cyclopropane (455) (entry 4) undergoes the cyclodimerization in milder conditions to afford the corresponding dispirooctane 459 in good yield [117,118a], while (difluoromethylene)cyclopropane (456) required higher temperatures to afford the cyclodimer 460 in low yield (entry 5) [9]. 

Apparently, the dimerization of 4 is considerably more facile than that of MCP or BCP, resembling those of (dichloromethylene)cyclopropane (455) and radicophilic olefins with a capto-dative substitution pattern [125], some of which are known to cyclodimerize even at room temperature. Indeed, the capto-datively substituted methylenecyclopropane 85 undergoes the homodimerization at 60 °C (Scheme 65) [126]. 

The most recent strategy to prepare [3]radialenes is the treatment of 1,1-dihaloalkenes with activated nickel. Thus, the aryl-substituted [3]radialenes (Z,E,E)-30 and (E,E,E) 30, 27 and 32 were obtained together with the corresponding butatrienes (29, 28, 31) from the 1,1-dibromo- or 1,1-dichloroalkenes with the help of nickel activated by ultrasound (Scheme 4)11. It is worth mentioning that the mixed-substituted radialene 33 was produced, when the nickel carbenoid derived from 9-(dichloromethylene)xanthene was generated in the presence of butatriene 2811. 

Despite the large body of literature discussing the preparation and reaction chemis try of dichloromethylene in solution, very few reports of the isolation of the molecule have appeared. The technique of forming Group IV dihalides from the reduction of the tetrahalide with the metal has proved to be of great utility for production of SiX2 and GeX2, but has not been successful in the case of carbon. 

Examples have also been reported in which glyconolactones are olelinated generating exoenitols (Fig. 10) for example by methylenation (Tebbe reaction),20 difluoromethylenation,21 and dichloromethylenation,22 the Wittig olefination.23... 

ClgH20Cl2N2O7 l-(5-0-Acetyl-2,3-0-isopropylidene-)8-D-ribofurano-syl)-5,6-(dichloromethylene)-5,6-dihydro-3-methyl-thymine (AIMCTY)157... 

The presence of a dichloromethylene group at the anomeric center of 82 facilitates proton abstraction at C-3 by a strong base (77), aifording the 4-deoxyglycos-3-ulose derivative 83. Reduction of the dichloromethylene group by Raney nickel gave a 1-C-methyl derivative with high stereospecificity, which opens the way to a series of 2,5-anhydro-l-deoxyalditols. Compound 83 was the key intermediate for the synthesis (78) of tosyl L-(+)-epi-muscarine (84a) and tosyl L-(+)muscarine (84b). 

Serretti R, Core P, Muti S, Salaffi F. Influence of dichloromethylene dipho-sphonate on reactive oxygen species production by human neutrophils. Rheumatol Int 1993 13 135-138. 

Phosphorane, (dichloromethylene) TRIPHENYL-1, 46, 33 Phosphorus pentachloride, for conversion of D,L-10-camphorsulfonic acid to acid chloride, 46,14 reaction with styrene, 46, 99 Photolysis of substituted stilbenes to phenanthrenes, 46, 91... 

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