- Synthesis of novel C2-symmetric ligands based on (R,R)- and (S,S)- diphenyl-1,3-propanediol
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A range of novel C2-symmetric dioxygen and dinitrogen ligands can readily be obtained through the interconversion of the parent 1,3-diphenyl- 1,3-propanediol enantiomers which are, in turn, accessed in good yields via a Sharpless asymmetric epoxidative resolution.
- Roos, Gregory H. P.,Donovan, A. Richard
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p. 991 - 1000
(2007/10/03)
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- A diastereoselective synthesis of (dl)-1,3-diphenyl-1,3-propanediamines
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A large-scale and practical synthesis of (dl)-1,3-diphenyl-1,3-propanediamine (1) has been achieved by a highly diastereoselective phenylcerium dichloride addition to 1-tert-butoxycarbonyl-4,5-dihydro-5-phenylpyrazole (3). Alkylcerium addition reaction to the corresponding 5-alkyl substituted 1-Boc-4,5-dihydropyrazoles was less satisfactory mainly giving ring-cleaved products. Further elaboration of the diamine 1 to the N-substituted derivatives 8a-f bearing N-methyl, N-ethyl, N-isopropyl, N-neopentyl, N-benzyl, and N-mesitylmethyl groups is described.
- Denmark,Kim
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p. 229 - 234
(2007/10/02)
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- Carbanion-Accelerated Claisen Rearrangements. 8. Phosphonamide Anion-Stabilizing Groups
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The utility of various phosphonamide groups has been examined in the context of the carbanion-accelerated Claisen rearrangement (CACR).An extensive survey has identified the N,N'-dibenzyl-1,3,2-diazaphospholidine group 11 to be optimal in the ease of construction of the CACR precursors and the facility and stereoselectivity of the rearrangement.Using n-butyllithium as the base, the phosphonamides rearranged readily at -20 deg C with complete regioselectivity and in good yield (74-79percent).The phosphonates also showed a high level of diastereoselectivity (>95percent de) but the yield from the (Z)-2-butenyl precursor (anti product) was only 45percent.A chiral N,N'-dibenzyl-1,3,2-diazaphospholidine 12 derived from trans-1,2-cyclohexanediamine was examined.Although the CACR proceeded very cleanly (71-85percent) and with high internal selectivity (94percent de), the relative asymmetric induction was poor (16-20percent de).This was also the case for a chiral N,N'-dibenzyl-1,3,2-diazaphosphorinane 15 derived from (R,R)-1,3-diphenyl-1,3-propanediamine and N,N'-dibenzyl-1,3,2-diazaphosphepine 16 derived from 6,6'-dimethyl-2,2'-diaminobiphenyl.The characteristic features of the CACR were compared with the aryl sulfone and phosphonate versions.
- Denmark, Scott E.,Stadler, Heinz,Dorow, Roberta L.,Kim, Jung-Ho
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p. 5063 - 5079
(2007/10/02)
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