Synthesis of spiro chromanone sandwiched 15,16,18 membered (Z)-dioxo cycloalkenes by ring closing metathesis and homodimers of 8-allyl-7-((6-bromoalkyl) oxy) spirochroman-4-ones by cross metathesis

Abstract

Novel spiro chromanone sandwiched 15,16,18 membered (Z)-1,7-dioxo cycloalkenes by Ring Closing Metathesis (RCM) and homodimers of 8-allyl-7-((6-bromo alkyl)oxy) spirochroman-4-ones by Cross Metathesis (CM) were synthesized from simple starting materials 2,4 dihydroxy acetophenone, allyl bromide, and dibromo alkanes. Spiro chromanone is chosen as the core moiety to be incorporated owing to its medicinal and pharmacophoric properties. The concept of molecular hybridization was adopted for the synthesis of compounds 18–26 using Ring Closing Metathesis as a key step. Intermediates 6,7,8 were alkylated with dibromo alkanes to obtain the substrates for RCM and CM, respectively. The dimer dienes 9–17 were made to undergo RCM and the bromo alkyl intermediates 27–34 were made to undergo CM to get homodimers 35–42.

Graphical Abstract

Keywords:

• Cross metathesis
• macrocycles
• molecular hybridization
• ring closing metathesis
• spiro chromanones

Acknowledgments

Author Prathima K is thankful to the Department of Science and Technology, New Delhi, India for supporting this research under the scheme “Disha programme for women in science” (SR/WOS-A/CS-1051/2014) One of the authors D. Ashok would like to thank University Grants Commission, New Delhi, India for the award of BSR-Faculty Fellowship (No. F.18-2011/BSR). Author Ravinder Dharavath is grateful to CSIR, New Delhi for providing SRF Fellowship (File No. 09/132(0865)/2017-EMR-I).