@article {46251, title = { Phosphite-Catalyzed C-H allylation of azaarenes via an enantioselective [2,3]-Aza-wittig rearrangement }, journal = {Angewandte Chemie-International Edition}, year = {2019}, month = {AUG}, type = {Article}, abstract = {

A phosphite-mediated [2,3]-aza-Wittig rearrangement has been developed for the regio- and enantioselective allylic alkylation of six-membered heteroaromatic compounds (azaarenes). The nucleophilic phosphite adducts of N-allyl salts undergo a stereoselective base-mediated aza-Wittig rearrangement and dissociation of the chiral phosphite for overall C-H functionalization of azaarenes. This method provides efficient access to tertiary and quaternary chiral centers in isoquinoline, quinoline, and pyridine systems, tolerating a broad variety of substituents on both the allyl part and azaarenes. Catalysis with chiral phosphites is also demonstrated with synthetically useful yields and enantioselectivities.

}, doi = {10.1002/anie.201906681}, author = {Motaleb, Abdul and Rani, Soniya and Das, Tamal and Gonnade, Rajesh G. and Maity, Pradip} } @article {47594, title = {Phosphite mediated asymmetric N to C migration for the synthesis of chiral heterocycles from primary amines}, journal = {Chemical Science}, volume = {12}, year = {2021}, month = {JUL}, pages = {8996-9003}, type = {Article}, abstract = {A phosphite mediated stereoretentive C-H alkylation of N-alkylpyridinium salts derived from chiral primary amines was achieved. The reaction proceeds through the activation of the N-alkylpyridinium salt substrate with a nucleophilic phosphite catalyst, followed by a base mediated [1,2] aza-Wittig rearrangement and subsequent catalyst dissociation for an overall N to C-2 alkyl migration. The scope and degree of stereoretention were studied, and both experimental and theoretical investigations were performed to support an unprecedented aza-Wittig rearrangement-rearomatization sequence. A catalytic enantioselective version starting with racemic starting material and chiral phosphite catalyst was also established following our understanding of the stereoretentive process. This method provides efficient access to tertiary and quaternary stereogenic centers in pyridine systems, which are prevalent in drugs, bioactive natural products, chiral ligands, and catalysts.}, issn = {2041-6520}, doi = {10.1039/d1sc01217g}, author = {Rani, Soniya and Dash, Soumya Ranjan and Bera, Asish and Alam, Md Nirshad and Vanka, Kumar and Maity, Pradip} } @article {49622, title = {Phosphite mediated molecular editing via switch to meta-C-H alkylation of isoquinolines: emergence of a distinct photochemical [1,3] N to C rearrangement}, journal = {Chemical Science}, volume = {16}, year = {2025}, month = {JAN}, pages = {1809-1818}, type = {Article}, abstract = {

The isoquinoline core is present in one of the largest subsets of bioactive natural products. The multifunctional isoquinoline core exerts diverse bioactivity, resulting in the development of numerous isoquinoline-based drugs and molecules that are currently under clinical trials. We developed a new approach for phosphite-mediated [1,2] alkyl migration for an overall ortho-C-H alkylation via N-alkylation of isoquinoline. Tuning the phosphite-mediated protocol to switch the site selectivity would expedite direct and diverse multi-C-H bond functionalization. We report a new approach starting with a simple N-alkylation of isoquinoline with sterically and electronically diverse alkyl bromides for their phosphite-mediated photochemical [1,3] N to C rearrangement followed by a rearomatization sequence that leads to meta-C-H (C4) alkylation. Combined experimental and computational studies unveiled the emergence of an unprecedented C-N bond cleavage pathway from the singlet excited state of the enamine-type intermediate. Our radical bond-cleavage pathway favors substituted alkyl group migration that complements the recently successful meta-alkylation methods with smaller and more reactive electrophiles. This switch in site selectivity via tuning the phosphite-mediated protocol resulted in sequential C-H difunctionalization of isoquinoline including regiodivergent ortho, meta-dialkylations of isoquinolines.

}, issn = {2041-6520}, doi = {10.1039/d4sc07127a}, author = {Rani, Soniya and Ray, Anuj Kumar and Dewangan, Devendra Kumar and Patil, Nita Aruna Ramchandra and Aarthika, M. and Paul, Ankan and Maity, Pradip} }