@article {42732, title = {Synthesis and utility of new amine/nucleobase addition products of allenylphosphonates}, journal = {Tetrahedron}, volume = {62}, year = {2006}, month = {SEP}, pages = {10152{\textendash}10161}, type = {Article}, abstract = {

In the reaction of allenylphosphonates with amines/nucleobases, depending on the amine and the allenylphosphonate, either Z- or E-vinylphosphonate or allylphosphonate as a single isomer with a β-amino functionality was isolated. A simple route to phosphonates with a β-NH2 group is developed by direct reaction with ammonia. In reactions with adenine, three different modes of reaction, with one of them involving an unusual cyclisation, are observed. The utility of (enamino)allyl phosphonate products thus obtained in the synthesis of (enamino)-1,3-butadienes via Horner{\textendash}Wadsworth{\textendash}Emmons (HWE) reaction is also demonstrated.

}, doi = {10.1016/j.tet.2006.08.034}, author = {Swamy, K. C. Kumara and Balaraman, Ekambaram and Kumar, N. Satish} } @article {42733, title = {Unusual products in the reactions of phosphorus(III) compounds with N=N, C equivalent to C or conjugated double-bonded systems}, journal = {Journal of Chemical Sciences}, volume = {118}, year = {2006}, month = {NOV}, pages = {495{\textendash}501}, type = {Article}, abstract = {

The diversity of products in the reaction of diethyl azodicarboxylate (DEAD)/diisopropyl azodicarboxylate (DIAD) and activated acetylenes with PIII compounds bearing oxygen or nitrogen substituents is discussed. New findings that are useful in understanding the nature of intermediates involved in the Mitsunobu reaction are highlighted. X-ray structures of two new compounds (2-t-Bu-4-MeC6H3O)P (μ-N-t-Bu)2P+[(NH-t-Bu)N[(CO2]-i-Pr)(HNCO2-i-Pr)]](Cl-)(2-t-Bu-4-MeC6H3OH)(23)and [CH2(6-t-Bu-4-Me-C6H2O)2P(O)C(CO2Me)C-(CO2Me)CClNC(O)Cl] (33) are also reported. The structure of23 is close to one of the intermediates proposed in the Mitsunobu reaction.

}, doi = {10.1007/BF02703946}, author = {Swamy, K. C. Kumara and Balaraman, Ekambaram and Pavan, M. Phani and Kumar, N. N. Bhuvan and Kumar, K. Praveen and Kumar, N. Satish} } @article {42731, title = {Convenient chromatography-free access to enantio-pure 6,6{\textquoteright}-di-tert-butyl-1,1{\textquoteright}- binaphthalene-2,2{\textquoteright}-diol- its 3,3{\textquoteright}-dibromo, di-tert-butyl and phosphorus derivatives: utility in asymmetric synthesis}, journal = {Tetrahedron-Asymmetry}, volume = {18}, year = {2007}, month = {SEP}, pages = { 2037{\textendash}2048}, type = {Article}, abstract = {

A simple chromatography-free high-yielding synthesis of the hexane-soluble enantiopure 6,6'-di-tert-butyl-1,1'-binaphthalene-2,2'-diol 3 (6,6'-di-tert-butyl BINOL) using Friedel{\textendash}Crafts reaction on 1,1'-binaphthalene-2,2'-diol 1 (BINOL) is described. The enantiomeric purity was fully maintained in the reaction. Compound 3 has been used as an entry point for the convenient chromatography-free synthesis of 3,3',6,6'-tetra-tert-butyl BINOL 4 and 3,3'-dibromo-6,6'-di-tert-butyl BINOL 5. A straightforward route to enantiopure bisphosphites [(6,6'-R2C20H10O2)P]2[O2C20H10-6,6'-R2] [R = H 15, t-Bu 16] by simply reacting phosphorochloridite (6,6'-R2C20H10O2)PCl [R = H 20, t-Bu 6] with metallic sodium is highlighted. The identity of 15 and 16 as their selenium-oxidized products 17 and 18 (at phosphorus center) is confirmed by X-ray crystallography (17 in the enantiopure form and 18 as racemate). Various enantiopure phosphoramidites of the modified BINOL have been synthesized. It is established that even when the phosphoramidites derived from the unsusbstituted BINOL 1 fail to give an appreciable optical induction in the asymmetric reduction of acetophenone/phenacyl chloride, those derived from 3 do induce moderate chiral induction (up to 30\% ee in the case for acetophenone and 43\% ee in the case of phenacyl chloride), thus leaving scope for further improvement in ee for related reactions.

}, doi = {10.1016/j.tetasy.2007.06.028}, author = {Balaraman, Ekambaram and Swamy, K. C. Kumara} } @article {42730, title = {Hydrophosphonylation of activated alkenes and alkynes via fluoride ion activation in ionic liquid medium}, journal = {Tetrahedron}, volume = {65}, year = {2009}, month = {JUL}, pages = {7603{\textendash}7610}, abstract = {

A simple transition metal-free hydro/hydrothiophosphonylation of Baylis{\textendash}Hillman adducts, substituted allyl bromides, allenylphosphonates and alkynes, promoted by fluoride ion in ionic liquid, is described. Clear-cut evidence for fluoride activation of the phosphite via pentacoordinate phosphorus is provided for the first time. Also, in a comparative reaction, the product obtained was different from that from the palladium catalyzed one. Structures of key products are proven by X-ray crystallography.

}, doi = {10.1016/j.tet.2009.06.096}, author = {Balaraman, Ekambaram and Srinivas, Venu and Swamy, K. C. Kumara} } @article {42728, title = {Mitsunobu and related reactions: advances and applications}, journal = {Chemical Reviews}, volume = {109}, year = {2009}, month = {APR}, pages = {2551{\textendash}2651}, doi = {10.1021/cr800278z}, author = {Swamy, K. C. Kumara and Kumar, N. N. Bhuvan and Balaraman, Ekambaram and Kumar, K. V. P. Pavan} } @article {42715, title = {Alkynyl and phosphonyl substituted nucleobases: a case of thermally induced conformational polymorphism}, journal = {Crystal Growth \& Design}, volume = {11}, year = {2011}, month = {APR}, pages = {2302{\textendash}2310}, abstract = {

Substituted nucleobases with alkynyl and phosphonyl groups were investigated in the context of supramolecular interactions and possible use toward synthesis of nucleoside phosphonic acids (NPAs). The adeninyl compound (adeninyl-N-9)-CH2CH2CH2CH2C=CH exhibits conformational polymorphism as revealed by X-ray structures determined at 200 and 298 K. Interestingly, in the compound (adeninyl-N-9)-(CH2)15CH3, the long aliphatic carbon chain does not show disorder. A rather unusual bending of alkyl chain, likely due to C{\textendash}H{\textperiodcentered}{\textperiodcentered}{\textperiodcentered}O interactions, is observed in the case of the thymine compound (thyminyl)-CH2CH2CH2C=CH that possesses a terminal alkyne group. The powerful hydrogen bond acceptor property of the phosphoryl oxygen (P=O) does not perturb (unless assisted by other hydrogen bonding partners) the homo base-pairing in the structures of most of the phosphonyl substituted nucleobases studied.

}, doi = {10.1021/cg101737x}, author = {Swamy, K. C. Kumara and Allu, Srinivasarao and Srinivas, Venu and Balaraman, Ekambaram and Kumar, K. V. P. Pavan} }