65383-73-5Relevant academic research and scientific papers
Efficient synthesis of precocenes
Kulkarni,Paradkar
, p. 1555 - 1562 (2007/10/02)
Precocenes and related intermediates were synthesised in good yields using hydrogen peroxide, selenium dioxide and methylene chloride combination in the key step.
A NEW SYNTHESIS OF PRECOCENE II AND PRECOCENE III BASED ON THE PHOTO-FRIES REARRANGEMENT OF A SESAMOL ESTER
Miranda, Miquel A.,Primo, Jaime,Tormos, Rosa
, p. 1159 - 1166 (2007/10/02)
The photo-Fries rearrangement of the sesamol ester of 3-methylcrotonic acid (2) in the presence of potassium carbonate affords a mixture of the o-hydroxyketones (3c) and (3d).Basic cyclization of the latter leads to the chromanones (4c) or (4d), respectively.Treatment of 4c with alkoxide/alcohol results in the regioselective cleavage of the methylenedioxy ring, to give the corresponding 7-alkoxy derivatives (4e) or (4f).Subsequent methylation with methyl iodide gives to rise to 4a or 4b and final reduction/dehydration by conventional methods affords the target compounds Precocene II (1a) or Precocene III (1b).
Chromene derivatives and pesticidal composition comprising the same
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, (2008/06/13)
The invention relates to a process for the preparation of chromenes of the general Formula V STR1 (wherein R1 and R2 are hydrogen, optionally halogeno substituted C1-6 alkyl or aryl; R3 and R7 stand for hydrogen, halogen or C1-6 alkyl; R4 represents C1-8 alkyl, aryl, aralkyl or a group containing a carbonyl group; R5 and R6 stand for C1-10 alkyl, aryl, amino, hydroxyalkyl, alkoxyalkenyl, alkylmercaptoalkyl, acyl, carboxy or an ester group or a halogen atom; n is 0 or 1) which comprises (a) for the preparation of compounds, in which R5 and R6 stand for different groups, reacting a compound of the general Formula I STR2 with an approximately equimolar, preferably 0.8-1.5 molar amount of a reactant of the general Formula R5 --X-related to the amount of the compound of the general Formula I (wherein R5 has the same meaning as stated above X is halogen) and reacting the O-monosubstituted compound of the general Formula III STR3 (wherein R1 -R6 and n are as stated above) obtained with a 1.1-1.5 molar amount of a compound of the general Formula III (wherein R6 and X are as stated above); or (b) for the preparation of compounds, in which R5 and R6 stand for the same group, reacting a chromanone of the general Formula I (wherein R1 -R4 and m have the meaning as stated above) with a 2-3 molar amount of a compound of the general Formula R5 --X-related to the amount of the compound of the general Formula I (wherein R5 and X are as stated above), preferably in the presence of a base, a catalyst and a solvent, and thereafter reducing the O-substituted chromanone derivative of the general Formula III thus obtained (wherein R1 -R6 and n are as stated above) and dehydrating the chromanol derivative of the general Formula IV STR4 thus obtained (wherein R1 -R6 and n are as stated above) in acidic-aqueous medium. The compounds of the general Formula V are partly new and useful for the preparation of pesticides.
A Novel Synthesis of Precocenes. Efficient Synthesis and Regioselective O-Alkylation of Dihydroxy-2,2-dimethyl-4-chromanones
Timar, Tibor,Jaszberenyi, J. Csaba
, p. 871 - 877 (2007/10/02)
The reactions of trihydroxybenzenes 1a-c and 3-methylbut-2-enoic acid (2) in a zinc chloride/water/phosphoryl chloride system afford either the new trihydroxyphenylbutenone derivatives 3b,c or dihydroxy-2,2-dimethyl-4-chromanones 4a-c in good yields.Compounds 3b,c can be cyclized in high yields to 4b,c in 5percent sodium hydroxide solution.Regioselective O-alkylation of 4a-c leads to 5a-f in good yields.O-Alkylation of 5a-f, followed by reduction and dehydration, results in the formation of precocene 3 (7d) and its regioisomer 7a-c,e,f.Methylation of 4a-c gives 6g-i.Subsequent reduction and dehydration affords precocene 2 (7h) and its regiosiomers 7g,i.
