Novel Synthesis and Crystal Structures of Two α, α′-bis-Substituted Benzylidene Cyclohexanones: 2,6-Bis-2-nitro(benzylidene)cyclohexanone and 2,6-Bis-4-methyl(benzylidene)cyclohexanone
Year: 2011
Type: article
Abstract: Bis(substituted-benzylidene) cycloalkanones are very important synthetic precursors for synthesis of biologically active pyrimidine derivatives [ 1 , 2 ]. These compounds have gained lots of attention due to their uses as agrochemical, pharmaceutical, and perfume intermediates and as liquid crystal polymer units [ 3 – 5 ]. Many of these methods suffer, however, from side reactions giving the corresponding products in low yields [ 6 ]. Recently some new kinds of Lewis acids have been used but in some cases the yields are less than 38% [ 7 ]. We have recently described the use of poly(ethylene) glycol/AlCl 3 as a green and reusable system for the synthesis of α, α′-bis(substituted-benzylidene) cycloalkanones [ 8 ]. In recent study, the versatility of SnCl 4 and the environmentally benign nature of ethanol as a green, inexpensive, and accessible solvent encouraged us to couple them together and study their utility for aldol condensation. Comparing the other methods, our synthetic procedure for preparation of different α, α′-bis(substituted-benzylidene) cyclohexanones (Scheme 1 ) provides good yields for a vast variety of substituted aromatic aldehydes with both electron withdrawing and electron releasing groups furthermore. Also the simplicity of operation, lack of unexpected by-products and mild condition of temperature are the others advantages of this method [ 9 ]. In recent study for the first time we have used SnCl 4 as a mild, inexpensive and efficient catalyst for the synthesis of differents α, α′-bis(substituted-benzylidene) cycloalkanones (Scheme 1 ). Use of ethanol as a green solvent helped us to improve total yields and this new combination for the first time provided excellent conditions to obtain good single crystals for X-ray studies of some obtained α, α′-bis(substituted-benzylidene) cyclohexanones. Here we report the results of the X-ray crystallographic studies for (2 E ,6 E )-2,6-bis(4-methylbenzylidene)cyclohexanone ( 1 , Scheme 1 ) and (2 E ,6 E )-2,6-bis(2-nitrobenzylidene)cyclohexanone ( 2 ). Structures of some similar compounds have been reported earlier, for instance bis(3-nitro) [ 10 ] and bis(4-nitro) derivatives [ 11 ]. Interestingly, even for the very similar compounds there are no indications of isomorphism what can suggest that very weak interactions are responsible for crystal packing.
Institutions: Semnan University, Adam Mickiewicz University in Poznań
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,190
Funder: Semnan University
OpenAlex ID: W2016299749