02606nas a2200229 4500008004100000022001400041245015900055210006900214260000800283300001400291490000700305520174400312100002402056700003002080700001902110700002602129700002302155700002402178700002502202700001702227856013202244 2019 eng d a0897-475600aRemarkably distinct mechanical flexibility in three structurally similar semiconducting organic crystals studied by nanoindentation and molecular dynamics0 aRemarkably distinct mechanical flexibility in three structurally cFEB a1391-14020 v313 a

Distinct macroscopic mechanical responses of the three crystals of naphthalene diimide derivatives, 1Me, 1Et, and 1nPr, studied here are very intriguing because their molecular structures are very similar, with the difference only in the alkyl chain length. Among the three crystals examined, 1Me shows highly plastic bending nature, 1Et shows elastic flexibility, and 1nPr is brittle. A detailed investigation by nanoindentation and molecular dynamics (MD) simulations allowed us to correlate their distinct mechanical responses with the way the weak interactions pack in crystal structures. The elastic modulus (E) of 1Me is nearly an order of magnitude lower than that of 1Et, whereas hardness (H) is less than half. The low values of E and H of 1Me indicate that these crystals are highly compliant and offer a low resistance to plastic flow. As the knowledge of hardness and elastic modulus of molecular crystals alone is insufficient to capture their macroscopic mechanical deformation nature, that is, elastic, brittle, or plastic, we have employed three-point bending tests using the nanoindentation technique. This allowed a quantitative evaluation of flexibility of the three mechanically distinct semiconducting molecular crystals, which is important for designing larger-scale applications; these were complemented with detailed MD simulations. The elastic 1Et crystals showed remarkable flexibility even after 1000 cycles. The results emphasize that the alkyl side chains in functional organic crystals may be exploited for tuning their self-assembly as well as their mechanical properties. Hence, the study has broad implications, for example, in crystal engineering of various flexible, ordered molecular materials.

1 aDevarapalli, Ramesh1 aKadambi, Sourabh, Bhagwan1 aChen, Chun-Teh1 aKrishna, Gamidi, Rama1 aKammari, Bal, Raju1 aBuehler, Markus, J.1 aRamamurty, Upadrasta1 aReddy, Malla uhttps://library.ncl.res.in/content/remarkably-distinct-mechanical-flexibility-three-structurally-similar-semiconducting-organic01462nas a2200205 4500008004100000022001400041245010200055210006900157260000800226300001400234490000700248520074800255100001701003700002201020700001601042700002601058700002201084700002101106856012901127 2022 eng d a0022-326300aReady access to benzannulated [5,5]-oxaspirolactones using Au(III)-catalyzed cascade cyclizations0 aReady access to benzannulated 55oxaspirolactones using AuIIIcata cMAR a3025-30410 v873 a

This work showcases an unprecedented Au(III)-catalyzed cascade cyclization of 2-(4-hydroxyalkynyl)benzoates to access benzannulated [5,5]-oxaspirolactones related to biologically active natural products. This reaction proceeds through an initial 5-endo-dig mode of hydroalkoxylation of the alkynol segment to give the oxocarbenium species (via cyclic enol-ether) followed by the addition of carboxylate onto the oxocarbenium that delivers the oxaspirolactone scaffold. While testing this method's scope, we found that the steric and electronic environment of the hydroxyl group could alter the reaction pathway that delivers isochromenone through a competitive 6-endo-dig mode of attack of the carboxylate onto the tethered alkyne.

1 aMankad, Yash1 aThorat, Sagar, S.1 aDas, Pronay1 aKrishna, Gamidi, Rama1 aKontham, Ravindar1 aReddy, Srinivasa uhttps://library.ncl.res.in/content/ready-access-benzannulated-55-oxaspirolactones-using-auiii-catalyzed-cascade-cyclizations01308nas a2200193 4500008004100000022001400041245018800055210006900243260000800312300001400320490000700334520055400341100001700895700001700912700001800929700002600947700001500973856012600988 2023 eng d a0022-326300aRadical cascade cyclization of unactivated alkene-tethered indoles with aryldiazonium salt and sodium metabisulfite to access Azo- and Sulfonylated-2,3-Dihyro-1H-pyrrolo[1,2-a]indoles0 aRadical cascade cyclization of unactivated alkenetethered indole cJUN a9123-91290 v883 a

A method for the construction ofheterocyclic scaffold2,3-dihyro-1H-pyrrolo[1,2-a]indolesvia arylsulfonylradical-triggered cascade cyclization of unactivated alkene-tetheredindoles in the absence of any external photocatalyst has been developed.This protocol features easily accessible starting materials such assodium metabisulfite and aryldiazonium tetrafluoroborates at roomtemperature and offers good functional group compatibility, enablingthe introduction of various functionalized sulfonyl and azo groupsinto pyrrolo[1,2-a]indoles.

1 aKumar, Pawan1 aRai, Archana1 aKumar, Manish1 aKrishna, Gamidi, Rama1 aDas, Utpal uhttps://library.ncl.res.in/content/radical-cascade-cyclization-unactivated-alkene-tethered-indoles-aryldiazonium-salt-and01591nas a2200229 4500008004100000022001400041245014200055210006900197260000800266300001600274490000700290520076700297653001701064653001601081653001501097100002201112700002201134700002501156700002601181700002201207856013201229 2023 eng d a0022-326300aRegioselective synthesis of benzannulated [5,6]-oxaspirolactones via Cu(II)-catalyzed cycloisomerization of 2-(5-Hydroxyalkynyl)benzoates0 aRegioselective synthesis of benzannulated 56oxaspirolactones via cNOV a16915-169330 v883 a

Spiroketals and oxaspirolactones are widely found in biologically active natural products, serving as important structural motifs. In this study, we present a Cu-(II)-catalyzed cascade cycloisomerization of 2-(5-hydroxyalkynyl)-benzoates, enabling the regioselective synthesis of benzannulated [5,6]-oxaspirolactones containing an isochromen-1-one moiety. This strategy offers a rapid and efficient approach to access a diverse array of benzannulated [5,6]-oxaspirolactones. The methodology presented here showcases a broad substrate scope, delivering good yields and scalability up to gram scale. The structures of the oxaspirolactones were unequivocally confirmed through single-crystal X-ray analysis and by analogy using H-1 and C-13-{H-1} NMR data.

10aConstruction10aIsocumarins10aStrategies1 aThorat, Sagar, S.1 aShimpi, Sagar, P.1 aSambherao, Pooja, I.1 aKrishna, Gamidi, Rama1 aKontham, Ravindar uhttps://library.ncl.res.in/content/regioselective-synthesis-benzannulated-56-oxaspirolactones-cuii-catalyzed-cycloisomerization