Dithienylalkanes

Directed metalation of -deficient azaaromatics strategies of functionalization of pyridines, quinolines, and diazines, 52, 187 gem-Dithienylalkanes and their derivatives, 32, 83... 

Barker, J. M., gem-Dithienylalkanes and Their Derivatives, 32, 83 The Thieno-pyridines, 21, 65. 

Electropolymerization with formation of conducting polymers 86CJC76. gem-Dithienylalkanes, general review 82AHC(32)83. 

Catalytic synthesis of thiophene and alkylthiophenes 71KGS1299. Coordination compounds with thiophene derivatives as ligands 76MI1. Dithienylalkanes, synthesis of 82AHC(32)83. 

The main interest in t/ero-dithienylalkane derivatives in recent years has been in their use as synthetic intermediates, via reductive desulfurization, for a variety of aliphatic substances (notably carboxylic acids) and as sub-... 

The nomenclature for gem-dithienylalkanes is reasonably straightforward, the thiophene rings being described as substituents of the parent alkane. Compound 6 is thus 2,2-bis(2-thienyl)butane, and 7 is l-chloro-2,2-bis-(5-ethyl-2-thienyl)ethane. 

Dithienylalkanes occur in certain shale oils of high sulfur content. The compounds described4,5 are bis(5-methyl-2-thienyl)ethanes and -propanes, both with and without additional methyl groups in the thiophene rings 5,5 -dialkyl-2,2 -dithienylmethanes are also present. A patent6 refers to the use of l,l-bis(2-thienyl)ethane, 2,2-bis(2-thienyl)propane, and 2-hydroxy-phenylbis(2-thienyl)methane as antioxidants for mineral oils, but otherwise there seems to be no commercial use for simple dithienylalkanes. 

In the second class of synthesis two thiophene rings become joined through a carbon atom that is already a substituent of one of them by this means symmetrically and unsymmetrically substituted products in the 2,2, 2,3, and 3,3 series are available. Three main reaction types have been employed in this approach. In one of these a thiophene is alkylated with a thenyl halide (Eq. 3). Friedel-Crafts acylation of a thiophene by a thenoyl chloride or thenoic acid followed by reduction of the resulting dithienyl ketone provides a second route in this category. The last and most versatile synthesis in this class involves reaction of a thienyllithium (or Grignard reagent) with a thienylaldehyde or thienyl ketone reduction of the carbinol (see Eq. 2) then gives the dithienylalkane. 

A more detailed survey of these reactions will now be given the section concludes with an account of some other, less general reactions that have led to dithienylalkanes. 

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