1.1- Dihalides methylene chloride

In the second reaction, the dihalide (methylene chloride) may react with 2 benzene rings to yield a diphenyl compound. Since benzene is in excess this reaction will take place. The second reaction is presented in figure B and the product is diphenylmethane. 

This binuclear photooxidative addition reaction is general for a number of halocarbons (Figure 3). While DCE and 1,2-dibromoethane react cleanly to give the dihalide metal dimers and ethylene, substrates such as bromobenzene or methylene chloride react through an alkyl or aryl intermediate. This intermediate reacts further to yield the dihalide d2-d2 metal complexes. 

The organic dihalides most often used are those that are commercially available such as methylene chloride, ethylene dichloride, propylene di-chloride, glycerol dichlorohydrin, dichloroethyl ether, dichloroethylformal, and triglycol dichloride. The most reactive chloro-compounds are the primary ones and these are the most commonly used. 

A convenient preparatory method is to form the tertiary phosphine molybdenum hexafluoride complex in methylene chloride at -60°C. On heating such complexes, R3PF2-type compounds are liberated (6.510). Hydrogen fluoride adds to alkylphosphonous dihalides (6.511). Fluorophosphoranes are also obtained from diphosphines (6.538 below), or by halogenation of R2NPF2 -type compounds (7.107). 

The reaction of an alkene with Br or Cl occurs rapidly at room temperature. The reaction is usually carried out in carbon tetrachloride or methylene chloride as solvent. The product is called a vicinal (Latin, vicinalis, neighboring) dihalide. Only one product forms. 

Other phosphorus compounds, e.g. PBrs, mixtures of PBrs and Br or PCI3/CI2 and phenyltetra-chlorophosphorane (PhPCU) have been used to convert amides to imidoyl halides. The formation of imidoyl halides proceeds under mild conditions by action of triphenylphosphine/CCU or triphenylphos-phine dihalides on secondary amides or ketoximes. The work-up procedure can be facilitated by use of polymer-supported triphenylphosphine/CCU. By the action of POCI3, phenyl- or methyl-phos-phonic acid dichloride on aminocarboxylic acid thiol esters in the presence of triethylamine the imidoyl chlorides (205 equation 114) are formed in moderate to good yields. The mechanism of this reaction has not been established. The methylene dialkylchlorophosphorane (206 equation 115) allows the conversion of secondary aromatic amides to imidoyl chlorides under very mild conditions. ... 

It has also been suggested to manufacture heliotropin starting from catechol (J. Gen. Chem., USSR, 1938, 8, 1975). This method involves a 3-step process which comprises 1) the preparation of methylenedioxybenzene from catechol, 2) the conversion of methylenedioxybenzene with paraformaldehyde and hydrogen chloride to heliotropyl chloride and 3) the reaction of the latter with hexamethylenetetramine in ethanol to obtain heliotropin with an overall yield of 11—28 % based on catechol. An improvement in the yield of step 1), and thus overall yield, can be obtained by employing a process for preparation of methylenedioxybenzene from catechol as described in U.K. patent specification 1,097,270 which involves the reaction of catechol with a methylene dihalide under alkaline conditions in the presences of a highly polar, aprotic solvent. 

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