Oxidative cyclisation and methylene insertion in 1 , 3-indandione derivatives . The mechanistic studies

Abstract Dimethyl sulphoxide activated by acetic-anhydride introduces methylthiomethyl group into phenols,oxidises certain medicinally useful secondary alcohols to their corresponding ketones and brings about oxidative rearrangements in different substrates.It converts 4-hydroxy coumarins and dicoumarols,under varying conditions,to a variety of products of both pharmaceutical and mechanistic interest.


Introduction
Dimethyl sulphoxide acetic anhydride, a versatile reagent has been a subject of reviews and monographs [1][2][3][4][5] with a wide range of chemical applications. It brings about oxidation of certain medicinally useful secondary alcohols 6 (Xa), oxidative -rearrangements 7, , oxidative degradation and oxidative cyclisations in different β -diketones depending upon the reaction conditions and structure of the diketone . This reagent also converrs 4-hydroxy coumarins and its 3substituted derivatives , under varying conditions , to a variety of products of both mechanistic and chemical interest 8,9 .
DMSO alone has been used as a reagent.It brings about methyl thiomethylation in barbituric acid 10 (Xb)and ylide formation in oxaxinones. When interacted with N,N-dimethyl analine in presence of FeCl3,it leads to the synthesis of N,N-Dimethyl Quinone-Imonium cations 11 (Xc).
In view of this it was considered worth to investigate the reactions of DMSO/Ac2O reagent or DMSO alone with 1,3indandione under varying conditions.
I S S N 2 3 2 1 -807X V o l u m e 1 3 N u m b e r 2 J o u r n a l o f A d v a n c e s i n c h e m i s t r y 5990 | P a g e A p r i l 2 0 1 7 Objective of the Research:-To synthesise novel compounds and investigate their properties applicable and beneficial to society in daytoday life.

Results and discussion
The reaction between 1,3-indandione and DMSO-acetic anhydride reagent when carried out at water bath temperature, reaches completion in 12 hours .Work up through removal of the reagent under vacuum followed by chromatography afforded compounds (2) and (3) The water-soluble, constituent was readily identified as the ylide.
(2) on the basis of its m.p. and spectral data which were in full agreement with those reported for this commpound.
The other compound ,m.p.255 0 c isolated from this reaction was characterized as the oxidative cyclisation product (3) . DMSO alone has also been used as a reagent yielding a number of products with different substrates under varying conditions.when 1,3-indandione was refluxed with this reagent at 180 0 C for 5 hours and workup through addition of water afforded a single pale yellow coloured solid identified as poly(methylene-bis)-1,3-indandione (5) which provides an alternate procedure by for the synthesis of tetrad (5).The compound did not melt upto 355 0 C ,so its mass spectrum could not be recorded and was found devoid of sulphur.However,on the basis of elemental analysis its molecular formula was found C39H24O8 which indicates participation of four indandione nuclei in it.The remaining three carbon atoms must have been derived from DMSO most likely in the form of methylene groups and was assigned the structure (5) The pmr spectrum of this compound recorded in CDCl3and DMSO-d6,shows a sharp singlet equivalent to two protons at δ 8.26 which is assigned to two terminal methine protons.Apart from the multiplet spread over the aromatic region,the spectrum shows two singlets at δ 1.23 and 2.09 equivalent to four and two protons respectively.The former was assigned to the two terminal protons and latter to the two central protons.
Methylene insertion has also been observed when 1,3-indandione was condensed with formaldehyde in presence of 2-3% of alkali carbonates to yield 2,2 / -methylene bis-1,3-indandione (6) and when the same reaction was carried out in presence of primary amines,it results in the formation of 2-spiro-indan-1,3-dione(7) indicating the involvement of methylene insertion in the adduct. The mechanism proposed for the formation of (6)

Materials and General information
Solvents used were of AR grade. DMSO was carefully dried according to the standard procedure. 1,3-indandione has been used as substrate.All reactions were monitored by TLC plates precoated with Silica gel Si60 F254 . Melting points were recorded on Tempo block melting point apparatus and are uncorrected.

Conclusion
Dimethyl sulphoxide has been used as reagent in presence of different activators or alone under different conditions.Its interaction with 1,3-indandione,under varying,conditions afforded a series of compounds of both chemical and mechanistic interest.Spectral studies revealed the incorporation of methylene groups or oxidative cyclisation in different products of synthetic importance.Silica-gel used for chromatographic techniques worked as a good adsorbent and showed better resolution than other adsorbents.