Indenes special

It is finally of interest to consider the solvolytic chemistry of 3,4-unsaturated and 3,4-benzo 2-bicyclo[3.1.0]hexyl systems. These are of special interest because they are sources of homologs of the antiaromatic cyclopentadienyl and inden-l-yl cations and as such should be destabilized antihomoaromatic systems. 

Several less common polymers with saturated carbon chain backbone are commercially available and have special practical applications. For example, indene obtained from the coal-tar oil by-products of coking operations can be polymerized by the addition of H2SO4 to form a linear hydrocarbon type polymer with relatively low DP [1-3]. The polymerization of coumarone from the same source generates a similar product, which is used in coatings, adhesives, etc. 

Rhodapon SM Special cosurhictant, friit coalings Rhodapon SM Special cosurMctanl, polymeric coalings Rhodapon SM Special coumarene-indene, duminum paints Cumat P-10 Cumat P-25 Cumai R-21 Cumat R-27,10° Cumat R-29, 10°... 

The reaction of acetylene in a glow discharge in a specially constructed reaction tube yields vinylacetylene, diacetylene, benzene, phenylacetylene, styrene, and indene as the major volatile products. The formation of these products can be most economically rationalized by assuming that the dimerization of acetylene to cyclobutadiene is the first reaction step. 

In the range of aromatic resins, a special significance is held by the modification with phenolic or phenol-formaldehyde resins. Unsaturated aromatic fractions (styrene-indene, indene-coumarone), mixed with phenol polymerize in the presence of Lewis or Bronsted acids (H2SO4, HCl, AICI3, or activated zeolites). Having removed the nonpolymerizable fraction, two fractions can be separated a liquid one (isolated by vapors bubbling) and another, solid, one. Both fractions... 

There are several phase transfer cyclopropanation reactions which deserve special comment. For example, addition of dichlorocarbene to the conjugated carbon-carbon double bond of styrene systems goes in excellent yield. Addition of dichlorocarbene to 1,2-dihydronaphthalenes [24] and to indenes [23] led to the expected 1,1-dichlorocyclopropane adducts. Heating the 1,1-dichlorocarbene adducts of indenes with ethanolic KOH provides an efficient route to 2-chloronaphthalene derivatives [23] (see Eq. 2.14). 

---