18791-95-2Relevant articles and documents
Synthesis of Thieno--, -- and --thiophenes and Thieno--, -- and --thienopyrimidin-7(6H)-ones Starting from Thiophene
Hawkins, David W.,Iddon, Brian,Longthorne, Darren S.,Rosyk, Peter J.
, p. 2735 - 2744 (2007/10/02)
3-Bromo-, 3,5-dibromo- and 3,4,5-tribromo-2-thienyllithium have been prepared by bromine ->lithium exchange and converted into a number of thiophene derivatives, including the corresponding 2-carbaldehydes.The aldehydes have been converted into the corresponding thiophene-2-carbonitriles.Metallation of 2,5-dibromo- or 2,4,5-tribromo-thiophene with LDA occured at a vacant 3-position but the resulting 3-lithiated thiophenes rearranged (mechanism discussed) to 3,5-dibromo- and 3,4,5-tribromo-2-thienyllithium, which were quenched with various electrophiles.Attempts to dilithiate 2,5-dibromothiophene with LDA were unsuccessful. 3,4-Dibromo-2,5-dilithiothiophene was prepared from 2,3,4,5-tetrabromothiophene but it failed to yield the 2,5-dicarbaldehyde with N,N-dimethylformamide.The title thienothiophenes were prepared by reaction of a 3-bromothiophene-2-carbaldehyde, a 2-bromothiophene-3-carbaldehyde (prepared by bromination of a thiophene-3-carbaldehyde) or a 4-bromothiophene-3-carbaldehyde, or a corresponding nitrile, with ethyl 2-sulfanylacetate or 2-sulfanylacetamide.Thienothiophenes carrying an o-aminocarboxamide substitution pattern gave the title thienothienopyrimidinones with triethyl orthoformate.
