Iodine-Alumina Catalyzed Aza- Michael Addition under Solvent Free Conditions

Saikia, Monmi; Kakati, Dwipen; Joseph, Maria Stalin; Sarma, Jadab C.

doi:10.2174/157017809790442961

Cited by 13 publications

(3 citation statements)

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“…The results obtained using existing methods were not satisfactory. We therefore tried some new catalysts for this conversion including iodine-alumina because of our previous experience of using iodine as an inexpensive, nontoxic, readily available catalyst in many other reactions [ 40 - 44 ]. Due to stringent and growing environmental regulations, the chemical industry needs the development of more eco-compatible synthetic methodologies [ 45 ].…”

Section: Introductionmentioning

confidence: 99%

Microwave assisted solvent free synthesis of 1,3-diphenylpropenones

Kakati

Sarma

2011

Chemistry Central Journal

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Background1,3-Diphenylpropenones (chalcones) are well known for their diverse array of bioactivities. Hydroxyl group substituted chalcones are the main precursor in the synthesis of flavonoids. Till date various methods have been developed for the synthesis of these very interesting molecules. Continuing our efforts for the development of simple, eco-friendly and cost-effective methodologies, we report here a solvent free condensation of aryl ketones and aldehydes using iodine impregnated alumina under microwave activation. This new protocol has been applied to a variety of substituted aryl carbonyls with excellent yield of substituted 1,3-diphenylpropenones.ResultsDifferently substituted chalcones were synthesized using iodine impregnated neutral alumina as catalyst in 79-95% yield in less than 2 minutes time under microwave activation without using any solvent. The reaction was studied under different catalytic conditions and it was found that molecular iodine supported over neutral alumina gives the best yield. The otherwise difficult single step condensation of hydroxy substituted aryl carbonyls is an attractive feature of this protocol to obtain polyhydroxychalcones in excellent yields. In order to find out the general applicability of this new endeavor it was successfully applied for the synthesis of 15 different chalcones including highly bioactive prenylated hydroxychalcone xanthohumol.ConclusionA new, simple and solvent free method was developed for the synthesis of substituted chalcones in environmentally benign way. The mild reaction conditions, easy work-up, clean reaction profiles render this approach as an interesting alternative to the existing methods.

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Section: Introductionmentioning

confidence: 99%

Microwave assisted solvent free synthesis of 1,3-diphenylpropenones

Kakati

Sarma

2011

Chemistry Central Journal

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“…Saikia et al previously showed that I 2 can be supported onto alumina and used for other aza-Michael additions. This approach was therefore considered and further investigated (Saikia et al, 2009). Acidic alumina (i.e., without I 2 ), used as received, was found to have no catalytic ability (entry 5, Table 1), giving similar results to the no catalyst system (entry 1) with the exception of a slight increase in the isomerization of DMI to DMMes.…”

Section: Resultsmentioning

confidence: 99%

Improving the Post-polymerization Modification of Bio-Based Itaconate Unsaturated Polyesters: Catalyzing Aza-Michael Additions With Reusable Iodine on Acidic Alumina

et al. 2019

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Bio-based platform molecules such as itaconic, fumaric, and muconic acid offer much promise in the formation of sustainable unsaturated polyester resins upon reaction with suitable diols and polyols. The C=C bonds present in these polyester chains allows for post-polymerization modification and such moieties are conventionally utilized in curing processes during the manufacture of coatings. The C=C modification sites can also act as points to add useful pendants which can alter the polymers final properties such as glass transition temperature, biodegradability, hardness, polarity, and strength. A commonly observed modification is the addition of secondary amines via an aza-Michael addition. Conventional procedures for the addition of amines onto itaconate polyesters require reaction times of several days as a result of undesired side reactions, in particular, the formation of the less reactive mesaconate regioisomer. The slow reversion of the mesaconate back to itaconate, followed by subsequent amine addition, is the primary reason for such extended reaction times. Herein we report our efforts toward finding a suitable catalyst for the aza-Michael addition of diethylamine onto a model substrate, dimethyl itaconate, with the aim of being able to add amine onto the itaconate units without excessive regioisomerization to the inactive mesaconate. A catalyst screen showed that iodine on acidic alumina results in an effective, heterogeneous, reusable catalyst for the investigated aza-Michael addition. Extending the study further, itaconate polyester was prepared by Candida Antartica Lipase B (CaL-B) via enzymatic polytranesterification and subsequently modified with diethylamine using the iodine on acidic alumina catalyst, dramatically reducing the required length of reaction (>70% addition after 4 h). The approach represents a multidisciplinary example whereby biocatalytic polymerization is combined with chemocatalytic modification of the resultant polyester for the formation of useful bio-based polyesters.

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“…The conjugate addition of azoles to methyl vinyl ketone in most cases occurs in the presence of acidic catalysts [8][9][10][11] or any other agents (ethylamine [12], molecular iodine on alumina [13], imidazolium salts [14]). There are some examples of the addition in dimethyl sulfoxide [15].…”

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confidence: 99%