Molecular iodine-catalyzed C3-alkylation of 4-hydroxycoumarins with secondary benzyl alcohols

A novel and efficient approach for the synthesis of new halo substituted 2-arylpyrazolo[4,3-c] coumarin derivatives

“…The use of iodine for synthetic purpose has gained significant importance. The negligible toxicity associated with iodine, in conjunction with ease of handling, readily availability, low cost and mild reaction conditions employed has resulted in its application in an increasing number of diverse transformations [18][19][20][21][22][23][24][25][26][27][28]. In continuation of our research programme using I2/DMSO as an efficient catalytic system for oxidation of pyrazoline to pyrazole [29], deallylation and preparation of flavones from 2'allyloxychalcones [30] and oxidation of dihydroflavone [31], here, we wish to report some new halo substituted 2arylpyrazolo [4,3-c]coumarins under mild condition.…”

Alcohols in direct carbon-carbon and carbon-heteroatom bond-forming reactions: recent advances

“…Benzyl [172][173][174][175][176][177] , allyl 175,[178][179][180][181][182][183][184] and propargyl 175,185,186 alcohols 6 were treated with various nucleophiles in the presence of I 2 (2-20 mol%) and formed different types of products (Scheme 24, Table 20). Tertiary alcohols underwent elimination of water in the absence of nucleophiles providing the corresponding alkenes such as 59 (R 1 = R 2 = R 4 = H), in high yields (Scheme 24).…”

Facile and Chemically Sustainable Catalyst‐Free Synthesis of Diverse 2‐Aryl‐4‐Alkyl/Aryl‐Pyrano[3,2‐c]chromen‐5(4H)‐Ones by One‐Pot Multicomponent Reactions at Room Temperature

“…Pyrano[3,2‐ c ]coumarins or pyrano[3,2‐ c ]chromen ‐ 5(4 H )‐ones are usually synthesized from the tandem reaction of commercially available 4‐hydroxycoumarins with varying suitable electrophiles such as 1,3‐diarylallylic compounds, propargylic alcohols and α,β‐unsaturated carbonyl compounds. All these earlier methods have certain merits of their own, but also suffer from various constraints such as heating and hazardous reactions conditions, use of strong acid conditions like I 2 ‐H 2 SO 4 and I 2 ‐AcOH, expensive transition metal catalysts like Ru, AuCl 3 –AgOTf in toluene and Bi(OTf) 3 , Ca(OTf) 2 /Bu 4 NPF 6 , stoichiometric loading of DDQ, toxic reagents,– and also use of less available catalysts, substrates, microwave irradiation, and with poor yields and regioselectivity . Hence, a search for simple and efficient, mild and clean, cost‐effective, high‐yielding, and environmentally benign routes to this class of biologically relevant O ‐heterocycles remains a valid exercise.…”