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n-Butyllithium (1 mol %)-catalyzed Hydroboration of Aldehydes and Ketones with Pinacolborane
양수진,Ashok Kumar Jaladi,김재호,Shankaraiah Gundeti,안덕근 대한화학회 2019 Bulletin of the Korean Chemical Society Vol.40 No.1
A practical and efficient protocol for the hydroboration of aldehydes and ketones using a pinacolborane and alkyl lithium system is demonstrated. A systematic evaluation showed that 1?mol % n-butyllithium afforded catalyzed hydroboration of aldehydes and ketones in a short reaction time under ambient conditions. Excellent yield, functional group tolerance, short reaction time, low catalyst loading, and gram-scale synthesis are the salient features of the proposed protocol.
Lithium tert-Butoxide-catalyzed Hydroboration of Carbonyl Compounds
김재호,Ashok Kumar Jaladi,김현태,안덕근 대한화학회 2019 Bulletin of the Korean Chemical Society Vol.40 No.10
We report the successful hydroboration of aldehydes and ketones with pinacolborane using 1?mol % lithium tert-butoxide under ambient conditions. The present protocol was applicable to various aldehydes and ketones, and the corresponding boronate esters and subsequent alcohols were obtained in good to excellent yields. In addition, this high-yielding practical method could be extended to the reduction of ester groups. Under optimized conditions, LiO tBu facilitate the hydroboration of ester groups quantitatively.
김현태,Ashok Kumar Jaladi,김재호,Shankaraiah Gundeti,안덕근 대한화학회 2019 Bulletin of the Korean Chemical Society Vol.40 No.1
Thermally expandable microspheres (TEMs) were synthesized via suspension polymerization using acrylonitrile as the major monomer. Methyl methacrylate and methacrylonitrile were used as supporting co-monomers, and 1,4-butanediol dimethacrylate was used as a crosslinking agent. In addition, cinnamonitrile (CN) and diethyl fumarate (DEF) were investigated as monomers to improve the expansion performance of the TEMs. However, the expandability of the TEMs using CN was diminished. When TEMs were prepared with DEF as the crosslinking agent, the expandability was highly affected. From the thermomechanical analysis of TEMs with various crosslinking agents, DEF showed better performance as crosslinking agent, yielding increased expansion properties. This is the first report using DEF as a TEM crosslinking agent.
Hyun Tae Kim,Ashok Kumar Jaladi,Yong Jin Lee,Duk Keun An 대한화학회 2020 Bulletin of the Korean Chemical Society Vol.41 No.2
Thermally expandable microspheres (TEMs) have widespread industrial applications. In this study, high heat resistant and largely expandable TEMs have been synthesized by suspension polymerization. Microspheres were prepared with acrylonitrile (AN) as the main monomer. Initial thermomechanical analysis of TEMs containing AN and methyl acrylate (MA) showed good thermal expansion, leading to the investigation of the polymerization using various monomers at variable weight ratios. TEMs with co-polymer AN, methyl methacrylate (MMA), and methacrylic acid (MAA) were investigated for the first time. They displayed wider heating range and larger expansion rate than the microspheres with MA monomer. The effect of varying amounts of monomer ratios on the thermal expansion behavior is discussed.
Im, So Hee,Shin, Won Kyu,Jaladi, Ashok Kumar,An, Duk Keun Elsevier 2018 Tetrahedron letters: the international organ for t Vol.59 No.24
<P><B>Abstract</B></P> <P>We demonstrate that copper diisobutyl-<I>t</I>-butoxyaluminum hydride, readily prepared from lithium diisobutyl-<I>t</I>-butoxyaluminum hydride and CuI, effectively and chemoselectively reduces tertiary amides over esters at ambient temperature, affording the corresponding aldehydes in excellent yields.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Designing of chemoselective reagent for amide reduction over ester is challenging. </LI> <LI> New reducing agent CDBBA was developed. </LI> <LI> The CDBBA exhibited good selectivity for tertiary amide reduction in the presence of ester. </LI> <LI> This method provides reduction of both aromatic and aliphatic substrates in excellent yields. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Shin, Won Kyu,Kim, Hanbi,Jaladi, Ashok Kumar,An, Duk Keun Elsevier 2018 Tetrahedron Vol.74 No.43
<P><B>Abstract</B></P> <P>Sodium hydride-promoted catalytic hydroboration of aldehydes and ketones with pinacolborane (HBpin) was examined, and 10 mol% of NaH was found to cause the HBpin to participate in hydroboration in a convenient and efficient manner at mild reaction conditions. Further chemoselective hydroboration of aldehyde over ketone functionality was also analyzed. In addition, no hydroboration was observed form ester, acyl chloride, amide, nitrile, alkene, alkyne, alkyl halide and epoxide functional groups indicate that present system (HBpin, NaH) is highly selective for aldehydes and ketones.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Joo Yeon,Shin, Won Kyu,Jaladi, Ashok Kumar,An, Duk Keun Elsevier 2018 Tetrahedron Vol.74 No.31
<P><B>Abstract</B></P> <P>t-Butoxy derivatives of DIBALH [lithium diisobutyl-<I>t</I>-butoxyaluminum hydride (LDBBA), sodium diisobutyl-<I>t</I>-butoxyaluminum hydride (SDBBA), and potassium diisobutyl-<I>t</I>-butoxyaluminum hydride (PDBBA)] were examined as chemoselective reducing agents of carbonyl compounds. Among them, PDBBA was found to be the most efficient for the reduction of aldehydes and ketones to the corresponding alcohols in the presence of ester, amide, and nitrile substituents at ambient temperature. In addition, the optimal conditions gave higher chemoselectivity for aldehydes in the presence of ketones.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Yi Jaeeun,Kim Hyun Tae,Jaladi Ashok Kumar,An Duk Keun 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.1
Transformation of relatively less reactive functional groups under catalyst-free conditions is an interesting aspect and requires a typical protocol. Herein, we report the synthesis of various primary, secondary, and tertiary amines through hydroboration of amides using pinacolborane under catalyst-free and solventfree conditions. The deoxygenative hydroboration of primary and secondary amides proceeded with excellent conversions. The comparatively less reactive tertiary amides were also converted to the corresponding N,N-diamines in moderate yields under catalyst-free conditions, although alcohols were obtained as a minor product.