Over the last decade, the exceptional power of chiral dirhodium(ii) carboxylate and carboxamidate catalysts has been demonstrated in a diverse array of enantioselective metal carbene transformations of diazocarbonyl compounds.[1] Aside from the superiority in diazo decomposition, a dirhodium(ii) complex with vacant coordination sites at the [*] Dr.

Dirhodium(II) tetrakis[N-tetrafluorophthaloyl-(S)-tert-leucinate], Rh2(S-TFPTTL)4, is an exceptionally efficient catalyst for enantioselective aminations of silyl enol ethers derived from acyclic ketones or alpha,beta-enones with [N-(2-nitrophenylsulfonyl)imino]phenyliodinane (NsN=IPh), providing N-(2-nitrophenylsulfonyl)-alpha-amino ketones in high yields and with enantioselectivities of up to 95% ee. The effectiveness of the present catalytic protocol has been demonstrated by an asymmetric formal synthesis of (-)-metazocine.

Abstract-The first catalytic enantioselective amination of silylketene acetals with (N-arylsulfonylimino)phenyliodinanes is described. The reaction of silylketene acetals derived from methyl phenylacetates with [N-(2-nitrophenylsulfonyl)imino]phenyliodinane (NsN=IPh) under the catalysis of dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate], Rh 2 (S-TCPTTL) 4 , proceeds in benzene at room temperature to give N-(2-nitrophenylsulfonyl)phenylglycine derivatives in high yields and with enantioselectivities of up to 99% ee.---* Corresponding author. Tel.: +81-117-063-236; fax: +81-117-064-981; e-mail: hsmt@pharm.hokudai.ac.jp.The catalytic asymmetric amination of silylketene acetals is one of the most straightforward methods for the preparation of enantioenriched α-amino esters.1,2 In 1999, Evans and Johnson described the first catalytic enantioselective amination of thioester silylketene acetals or silylketene aminals of acylpyrroles with azodicarboxylate derivatives, in which enantioselectivities up to 99% ee were achieved with the use of a Cu(OTf) 2 -bis(oxazoline) catalyst. 3,4Kobayashi and co-workers later reported that a AgClO 4 -BINAP system catalyzed the amination of the silylketene acetal of phenyl propionate with dibenzyl azodicarboxylate with good enantioselectivity (51% ee). 5 In this context, the aziridination of silylketene acetals followed by ring opening of the aziridine intermediate provides a prototypical approach to catalytic asymmetric synthesis of α-amino esters. 6 In 1994, Evans and co-workers reported the first copper(I)-catalyzed amination of silylketene acetals using [(p-tolylsulfonyl)imino]phenyliodinane (TsN=IPh, 2a) as a nitrene precursor, 7 and they concluded that this protocol does not represent a practical approach to the synthesis of α-amino esters. While high levels of enantiocontrol in aziridinations of alkenes have already been achieved using a variety of different chiral transition metal-catalysts, 8 the catalytic enantioselective amination reaction of silylketene acetals with (Narylsulfonylimino)phenyliodinanes has, to the best of our knowledge, not been reported. 9Very recently, we demonstrated that the enantioselective amination of silyl enol ethers derived from acyclic ketones or enones with [(2-nitrophenylsulfonyl)imino]phenyliodinane (NsN=IPh, 2b) catalyzed by chiral dirhodium(II) carboxylates provides N-(2-nitrophenylsulfonyl)-α-amino ketones with enantioselectivities of up to 95% ee.

A new route to the diarylheptanoid diospongins A and B was developed. The key step is a novel, one‐pot, sequential dirhodium(II) tetrakis[(S)‐3‐(benzo‐fused phthalimido)‐2‐piperidinonate] [Rh2(S‐BPTPI)4] catalyzed enantioselective hetero‐Diels–Alder/TMSOTf‐catalyzed Mukaiyama–Michael reaction process. The sign of the optical rotation of natural diospongin B was determined to be (+) and not (–) as was originally reported.

Abstract-Catalytic asymmetric syntheses of (-)-centrolobine and (-)-de-O-methylcentrolobine have been achieved, incorporating a hetero-Diels-Alder (HDA) reaction between 4-aryl-2-silyloxy-1,3-butadienes and phenylpropargyl aldehyde derivatives as a key step. The HDA reaction using dirhodium(II) tetrakis[(R)-3-(benzene-fused-phthalimido)-2-piperidinonate], Rh 2 (R-BPTPI) 4 , as a chiral Lewis acid catalyst provides exclusively cis-2,6-disubstituted tetrahydropyran-4-ones in up to 93% ee.