Desymmetrization of meso-N-sulfonylaziridines with chiral nonracemic nucleophiles and bases

Article abstract of DOI:10.1002/1522-2675(20010321)84:3<662::AID-HLCA662>3.0.CO;2-P

The cyclohexene-derived aziridine 7-tosyl-7-azabicyclo[4.1.0]heptane (1) reacts with Grignard reagents in the presence of chiral nonracemic Cu-catalysts to afford sulfonamides 3a-e in up to 91% ee under optimized conditions. No activation of the aziridine by Lewis acids is required. The reaction may be extended to other bicyclic N-sulfonylated aziridines, but aziridines derived from acyclic olefins, cyclooctene, and trinorbornene are unreactive under standard conditions. Exposure of 1 to s-BuLi in the presence of (-)-sparteine (2.8 equiv.) affords the allylic sulfonamide 31 in 35% yield and 39% ee. Under the same conditions, the aziridines 33 and 35 yield products 34 and 36 derived from intramolecular carbenoid insertion with 75 and 43% ee, respectively.

Full text of DOI:10.1002/1522-2675(20010321)84:3<662::AID-HLCA662>3.0.CO;2-P

662
Helvetica Chimica Acta ± Vol. 84 (2001)
Desymmetrization of meso-N-Sulfonylaziridines with Chiral
Nonracemic Nucleophiles and Bases
by Paul Müller* and Patrice Nury
Department of Organic Chemistry, University of Geneva 30, Quai Ernest Ansermet, CH-1211 Geneva 4
The cyclohexene-derived aziridine 7-tosyl-7-azabicyclo[4.1.0]heptane (1) reacts with Grignard reagents in
the presence of chiral nonracemic Cu-catalysts to afford sulfonamides 3a ± e (Scheme 3) in up to 91% ee under
optimized conditions (Table 2). No activation of the aziridine by Lewis acids is required. The reaction may be
extended to other bicyclic N-sulfonylated aziridines, but aziridines derived from acyclic olefins, cyclooctene, and
trinorbornene are unreactive under standard conditions (Scheme 5). Exposure of 1 to s-BuLi in the presence of
(
)-sparteine (2.8 equiv.) affords the allylic sulfonamide 31 in 35% yield and 39% ee (Scheme 6). Under the
same conditions, the aziridines 33 and 35 yield products 34 and 36 derived from intramolecular carbenoid
insertion with 75 and 43% ee, respectively.
Introduction. ± Aziridines are the N-analogues of epoxides, and as such, are
attractive intermediates for a variety of transformations affording N-containing
products [1]. In this context, the synthesis of chiral nonracemic aziridines is of
particular interest. However, although chiral aziridines are accessible via asymmetric
aziridination of olefins [2], the methods currently available are limited. Alternatively,
optically active products derived from ring opening of achiral aziridines are, in
principle, accessible via their enantioselective desymmetrization, in analogy with the
widely and successfully applied desymmetrization of achiral epoxides [3]. This latter
reaction may be effected via a-deprotonation [4], b-deprotonation [5], or via
nucleophilic ring opening under stoichiometric [6] and catalytic conditions [7]. Several
procedures for selective ring opening of aziridines by nucleophilic substitution are
known. N-Alkyl- or N-(arylalkyl)aziridines undergo ring opening in the presence of
catalytic amounts of lanthanide ions, in particular YbIII [8], and react with aromatic
amines in the presence of SnII or CuII catalysts [9]. Enantioselective opening of N-
alkylaziridines with up to 94% ee has been reported for their reaction with azido-
trimethylsilane (Me3SiN3) and a tridentate Schiff-base chromium complex [10]. A cata-
lytic method involving thiols in the presence of ZnEt2 and an optically active tartrate
for desymmetrization of N-acylated aziridines has recently been published [11]. Ring
opening of aziridines by organometallic reagents, in turn, has been known since 1985,
when Eis and Ganem reported the opening of N-alkylaziridines by organocuprates
under stoichiometric conditions in the presence of BF3 [12]. Subsequently, Baldwin et
al. found that N-sulfonated aziridines do not require BF3 to react with organocuprates
[13], and several applications of this observation appeared [14][15], including achiral
opening of N-phosphinylaziridines with organocuprates [16].
In the context of our ongoing research on catalytic aziridination of olefins [2a][17],
a certain number of chiral and meso-N-sulfonylaziridines were synthesized via RhII-

Helvetica Chimica Acta ± Vol. 84 (2001)
663
catalyzed reaction of olefins with PhIˆNTs. Surprisingly, however, when very electron-
rich olefins were used as substrates, N-sulfonylated pyrrolidines were isolated; these
were formally derived by ring opening of the putative intermediate aziridines to dipolar
species which, apparently, underwent cycloaddition to the olefin present in excess. The
aziridine opening was attributed to the presence of the electrophilic rhodium(II)
carboxylate or carboxamidate catalysts. This observation suggested the possibilty of
aziridine desymmetrization by chiral RhII catalysts, and experiments in this direction
were initiated. Although the original idea could not be realized, we found, in the course
of these investigations, conditions under which desymmetrization of N-sulfonated
aziridines occurred under catalytic conditions with organometallic reagents in the
presence of chiral Cu-complexes [18].
Results. ± Exploratory Experiments for Nucleophilic Ring Opening of Aziridines.
Exploratory experiments with the cyclohexene-derived aziridine 7-tosyl-7-azabicy-
clo[4.1.0]heptane (1) and Lewis acid catalysts revealed that rhodium(II) carboxylates
are not sufficiently electrophilic to effect ring opening of aliphatic aziridines. Thus, no
reaction occurred when 1 was exposed to nucleophiles such as azidotrimethylsilane
(Me3SiN3), trimethylsilanecarbonitrile, aniline, etc. in refluxing CH2Cl2 in the presence
of [Rh2(OAc)4]. NaN3 in DMF was effective at room temperature and in refluxing
MeCN, but addition of [Rh2(OAc)4] had no catalytic effect (Table 1). Me3SiN3 in
conjunction with [Cu(acac)2] (Hacac ˆ pentane-2,4-dione) or [Zn(tartrato)] afforded
ring-opened 2a [19] in refluxing MeCN, but the reaction required 7 to 12 d to go to
completion. Similarily, the [Cr(salen)] complex (H2salen ˆ bis(salicylidene)ethylene-
diamine) of Jacobsen and co-workers [7d,e][20] was not effective with Me3SiN3. These
results indicated that the presence of the strongly electron-attracting sulfonate group at
the N-atom of 1 decreases its basicity to such an extent that association with the
electrophilic catalyst was ineffective for opening of the aziridine ring. This hypothesis is
supported by the recent observation of Jacobsen and coworkers [10] that the more basic
N-benzyl-substituted aziridines react with Me3SiN3 with a chiral [Cr(Schiff base)]
catalyst at low temperature and with excellent enantioselectivity. Nevertheless, 1 did
react with Me3SiN3 and [TiCl2(OiPr)2], but the reaction took place via chloride attack
to afford 2b. Exposure of 1 to MeMgBr in the absence of catalyst resulted in formation
of the bromide 2c [21], suggesting activation of the aziridine by MgII. That Mg ions may
activate 1 was further demonstrated by conversion of 1 to 2c with MgBr2. The
possibility of effecting aziridine opening with Mg complexes was not further explored
at that time. However, addition of 10% of [Cu(acac)2] to MeMgBr resulted in
nucleophilic attack by the organometallic reagent, and 3a was obtained in 85% yield.
Cu-Catalyzed Desymmetrization of 1 with MeMgBr. The enantioselectivity of the
reaction was investigated with several chiral catalysts (see 4 ± 17; Fig.), which were
prepared according to literature procedures or in analogy to reported methods (for
references to 4 ± 14, see Exper. Part). The synthesis of phosphoramidite 13 derived from
8,8'-binol ([1,1'-binaphthalene]-8,8'-diol) is reported elsewhere [22]. The dihydroox-
azole ligand 16 was synthesized by reaction of (4S)-4,5-dihydro-4-isopropyl-a,a-
dimethyloxazole-2-methanol (19) with in situ prepared phosphorochloridite 18 [23]
(Scheme 2). Racemic biphenanthrenediol 20 was prepared by oxydative coupling of
phenanthren-9-ol with [CuCl2] [24] or with [CuCl(OH)] ´ TMEDA (N,N,N',N'-

664
Helvetica Chimica Acta ± Vol. 84 (2001)
Scheme 1a)
a) The relative configuration of 2a ± c and 3a is shown.
tetramethylethylenediamine) [25]. The enantiomers of 20 were separated either via
the cyclic phosphoramidite, derived from ( )-(S)-a-methylbenzylamine followed by
reduction with LiAlH4 [25], or according to the procedure described by Toda and
Tanaka [26]. The (S)-enantiomer of 20 was treated with diisopropylphosphoramidous
dichloride (21) [27] to afford the phosphoramidite 17.
Table 1. Electrophilic Catalysis in the Ring Opening of 1
Nucleophile
Catalyst
Solvent
Temp., time
Product
Yield/%
NaN3, 1.2 equiv.
NaN3, 1.2 equiv.
±
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
CH2Cl2
CH2Cl2
CH2Cl2
THF
Reflux, 24 h
Reflux, 24 h
Reflux, 12 d
Reflux, 7 d
Reflux, 12 d
Reflux, 7 d
08, 7 d
08, 2 d
08, 2 d
08, 6 h
08, 24 h
2a
2a
2a
2a
2a
2a
2a
2b
2b
2c
2c
2d
89
85
60
74
65
81
58
20
88
91
82
85
[Rh2(OAc)4], 10%
[Cu(acac)2], 10%
[Cu(acac)2], 20%
[Zn(tartrato], 10%
[Zn(tartrato)], 20%
[Zn(Et)2], 10%
[TiCl2(O-iPr)4], 10%
[TiCl2(O-iPr)4], 50%
±
Me3SiN3, 1.2 equiv.
Me3SiN3, 4.0 equiv.
Me3SiSN3, 1.2 equiv.
Me3SiN3, 4.0 equiv.
Me3SiN3, 1.2 equiv.
Me3SiN3, 1.2 equiv.
Me3SiN3, 1.2 equiv.
MeMgBr 1.2 equiv.
MgBr2, 1.0 equiv.
MeMgBr, 1.2 equiv.
±
THF
THF
[Cu(acac)2], 10%
08, 1 h
Aziridine opening was effected either with the isolable Cu complexes (Method A),
or by preparing the catalysts in situ by addition of 0.2 equiv. of the ligand of interest to
0.1 equiv. of [Cu(OTf)2] (Method B). The desymmetrizations were carried out by
addition of the organometallic reagent (1.0 equiv.) in THF at 08 to a THF solution
containing the aziridine 1 and the catalyst with a 10 :1 substrate/catalyst ratio. Table 2
summarizes the principal results. The effect of solvent, temperature, and origin of the
organometallic reagent has been reported in the preliminary communication [18]. The
results obtained with still other, less satisfactory ligands, will be reported elsewhere
[28].
Yield and enantioselectivity of the reaction depended not only upon the ligand, but
also upon the catalyst concentration, the counterion of the organometallic reagent
‡
‡
(MgX , Li ), and the solvent [18]. Under standard conditions, the highest ee of 79%
resulted with 16. The reaction conditions were, however, optimized with 8, which is
more readily accessible, and the ee increased from 55% under standard conditions to
91% (in THF with 30% of catalyst, addition of MeMgBr within 10 min). The principal

Helvetica Chimica Acta ± Vol. 84 (2001)
665
Scheme 2
Table 2. Desymmetrization of Aziridine 1 to 3a with MeMgBra)
Catalyst
Method
Time/h
Yield/%
ee/%b
Absolute configuration
[Cu(acac2]
4
5
6
A
B
B
A
A
A
A
A
A
A
A
B
B
A
B
B
B
1.0
2.0
2.0
2.0
2.0
2.0
1.5
1.5
3.0
1.5
2.0
2.0
1.0
1.5
2.5
2.5
1.5
85
73
84
71
75
89
52
89
75
78
65
73
64
78
81
59
69
±
±
52
29
13
0
(1S,2S)
(1S,2S)
(1S,2S)
±
7
8
55
91
28
12
13
50
31
42
12
21
79
49
(1S,2S)
(1S,2S)
(1S,2S)
(1S,2S)
(1S,2S)
(1S,2S)
(1R,2R)
(1S,2S)
(1R,2R)
(1S,2S)
(1R,2R)
(1S,2S)
8 (30%)c)
9a
9b
10
10
12
13
14
15
16
17
a) Conditions: MeMgBr (0.60 ml, 1.4m in THF/toluene), added dropwise to 1 (200 mg, 0.80 mmol) and catalyst
b
(0.080 mmol) in THF (2.0 ml) at 08. ) Determined by HPLC (Chiracel OD H column, hexane/iPrOH 9 : 1).
c) Optimized conditions [18].

666
Helvetica Chimica Acta ± Vol. 84 (2001)
Figure. Catalysts and ligands

Helvetica Chimica Acta ± Vol. 84 (2001)
667
side reaction was halide attack, leading to 2b or 2c, when MeMgCl or MeMgBr,
respectively, was used.
Desymmetrization of 1 with other Grignard Reagents. Variation of the structure of
the organometallic reagent was examined under standard conditions. Ligand 8 was used
in all cases, but, for some reagents, other ligands were also tested (Table 3). No ring
opening occurred with HCꢀCMgBr, H2CˆCHMgBr and H2CˆCHCH2MgBr, and
tBuMgBr under standard conditions, but Grignard reagents derived from primary and
secondary alkyl as well as aryl bromides reacted with acceptable yields ( ! 3a ± e, see
Scheme 3). The enantioselectivity was quite variable, however, but was not optimized
systematically. Surprisingly, while the MeMgBr opened aziridine 1 in the presence of 8
with a moderate selectivity of 55%, the corresponding reaction with PhMgBr afforded
only racemic product. Some induction occurred, however, with PhMgBr and 9b as
catalyst, but the absolute configuration at C(1) of the product was opposite of that
obtained with MeMgBr and 9b. Increased steric hindrance at the benzene ring as
exemplified with (mesityl)MgBr (mesityl ˆ 2,4,6-trimethylphenyl) resulted in in-
creased enantioselectivity, which culminated at 72% with 8. Other catalysts were tried
with PhMgBr, but the enantioselectivity was in all cases below 10%.
The absolute configuration of 3a resulting from the reaction with ligand 8 was
determined to be (1S,2S) by its conversion via reductive cleavage [29] to the amine 22
of known absolute configuration [30] (Scheme 4). For the phenyl-substituted
sulfonamide 3d, the free amine 23 with (‡)-(1S,2R)-configuration was synthesized
Scheme 3a)
a) The relative configuration of 3a ± e is shown. The absolute configuration of 3a is (1S,2S), and that of 3d is
(1R,2S) (see Scheme 4).
Table 3. Cu-Catalyzed Ring Opening of 1 with Grignard Reagentsa)
Nucleophileb)
Catalyst
Time
Product
Yield/%
ee/%
Absolute configuration
MeMgBr
MeMgBr
(Pentyl)MgBr
iPrMgBr
PhMgBr
PhMgBr
MesMgBr
MesMgBr
MesMgBr
MesMgBr
MesMgBr
MesMgBr
8
9b
8
8
8
9b
5
8
9a
10
12
14
2.0 h
2.0 h
2.0 h
1.5 h
2.0 h
1.5 h
3.0 h
3.0 h
2.5 h
2.5 h
2.5 h
3.0 h
3a
3a
3b
3c
rac-3d
ent-3d
3e
3e
3e
89
75
75
71
80
75
32
45
48
63
55
28
55
12
15
21
0
29
67
72
15
53
0
(1S,2S)
(1S,2S)
(1R,2S)
3e
3e
3e
68
a) Conditions, see Table 2. b) Mes ˆ 2,4,6-Trimethylphenyl.

668
Helvetica Chimica Acta ± Vol. 84 (2001)
Scheme 4
from 2-phenylcyclohexanone and sulfonated with TsCl [31]; comparison of the optical
rotation and the HPLC retention time of the thus-obtained sulfonamide revealed
(1S,2R)-3d that the phenyl-substituted sulfonamide resulting from reaction of 1 with
catalyst 8 was (1R,2S)-3d. The absolute configuration of the other sulfonamides was not
determined.
Reaction of Other Substrates with MeMgBr. Likewise, the aziridines 24 and 26
derived from cyclohexa-1,4-diene and cyclopentene, respectively, underwent Cu-
catalyzed ring opening in the presence of ligand 8 to afford the sulfonamides 25 and 27,
respectively, with modest enantioselectivities (Scheme 5). In contrast, the (Z)-oct-4-
ene-derived aziridine 28 was unreactive under the conditions of the reactions. Other
bicyclic and polycyclic aziridines such as 33 and 35 (Scheme 6) were equally unreactive.
The catalytic system was also applied to cyclohexene oxide (29), which reacted to give
trans-2-methylcyclohexanol (30) [32] in 50% yield, but the enantioselectivity with 8
was poor. The reaction is nevertheless remarkable, because it is catalytic with respect to
copper, and, unlike the epoxide opening with organolithium reagents, does not require
activation with BF3 [33]. Chiral heterocuprates have been shown to open 1 to give the
corresponding alcohols in at most 3.6% ee [32]. At this time, no attempt has been made
towards improvement of the selectivities of the reactions presented in Scheme 5.
Sparteine-Mediated Isomerization of N-Sulfonylaziridines to Allylic Sulfonamides.
The rearrangement of meso-epoxides in the presence of chiral bases to chiral allylic
alcohols is well-established. However, only a single communication on the analogous
isomerization of N-acylated aziridines to optically active allylic amines has been
published [34]. The reaction occurs in the presence of vitamin B12 as catalyst [5b]. It is
believed to involve nucleophilic ring opening by the CoI nucleophile to a CoIII
intermediate, which then undergoes reductive elimination to an allylic amide and
CoI. In contrast, N-sulfonylated- or N-phosphinoylated aziridines reportedly do not
rearrange to allylic amines in the presence of lithium amide bases [35].

Helvetica Chimica Acta ± Vol. 84 (2001)
669
Scheme 5
s
When 1 was exposed to BuLi in the presence of 2.8 equiv. of ( )-sparteine,
rearrangement occurred to the allylic N-(cyclohex-2-en-1-yl) amide 31 (35%, 39% ee)
and the N-(cyclohex-1-en-1-yl) amide 32 (31%) (Scheme 6). The aziridines 33 and 35,
in turn, rearranged to 34 (69%, 75% ee) and 36 (72%, 43% ee), respectively, both
derived from intramolecular carbene insertion. The a configuration of the sulfonamide
group in 34 was deduced from NOESYexperiments that indicated interactions between
the protons at the functionalized (C(1)) and the bridgehead positions on the b-side. The
absolute configuration of 36 was determined to be (R) by comparison of its optical
rotation and HPLC retention time with those of an independently prepared sample of
(R)-36. The reference compound (R)-36 was synthesized via bromination of
trinorbornene followed by carbonylation [36][37] to give 37. Racemic 37 was partially
resolved by recrystallization of its salt with (‡)-(R)-a-methylbenzylamine and
converted to the amine (R)-38 via Curtius degradation with diphenylphosphoryl azide
[38]. The optical rotation of (R)-38 established an ee of 53% ee, based on the f2D5 (S)-
38 [39] (see Exper. Part).
To our knowledge, these are the first base-induced rearrangements of sulfonylated
aziridines to allylic amides ever reported. The reaction appears to be analogous to the
corresponding rearrangement of epoxides [4][5], yields and enantioselectivities being

670
Helvetica Chimica Acta ± Vol. 84 (2001)
Scheme 6
in the same range. Further experiments to establish scope and limitations of this
reaction are in progress in our laboratory.
Discussion. ± The aziridine openings reported here involve enantioselective attack
of a chiral nucleophile at one of two enantiotopic centers. This concept differs, at first
glance, from that usually applied to desymmetrization of epoxides and aziridines based
on chiral electrophilic catalysts and achiral reagents, and bears more resemblance to the
Cu-catalyzed enantioselective addition reactions of Grignard [40] or dialkylzinc
reagents to enones [41] or vinyloxiranes [42]. However, there is substantial
experimental evidence that the catalyzed epoxide openings exhibit second-order
kinetics with respect to catalyst concentration, which indicates a bimetallic mechanism
for catalysis [43]. This suggests coordination of the nucleophile to the chiral catalyst
prior to nucleophilic attack. These observations are supported by density-functional
theory calculations that show coordination of the leaving group with the organometallic
reagent in nucleophilic displacements with lithium organocuprates [44]. These
observations should also apply to aziridine openings. Thus, in the electrophilic catalysis
for epoxide opening, the nucleophile is delivered from a chiral catalyst, and in the

Helvetica Chimica Acta ± Vol. 84 (2001)
671
nucleophilic catalysis of aziridine opening, the N-atom of the aziridine may be
coordinated to an electrophile, so that the mechanisms involved in these reactions are
probably not fundamentally different.
This work was supported by the Swiss National Science Foundation (Grant Nos. 20-52581.97 and 2027-
 Â
048156), by the European Commission for Science, Research, and Development (COSTAction D12), the Societe
Â
Á
Academique de Geneve (Fonds Marc Birkigt), and the University of Geneva. The authors are indebted to Mrs.
A. Pinto and J.-P. Saulnier for the NMR spectra, and to Ms. D. Klink for the mass spectra.
Experimental Part
General. All reactions were carried out under N2 by standard Schlenk techniques [45]. CH2Cl2 and MeCN
were dried over CaH2 and distilled. Et2O, THF, and toluene were dried over Na/benzophenone and distilled.
The other solvents were purchased from Fluka or Merck and used without purification. ( )-Sparteine ´ H2SO4 ´
5 H2O (Fluka) was extracted with base, and the free amine was distilled and stored under Ar at 788. Flash
chromatography (FC) [46]: silica gel 60 Merck 9385. TLC: Macherey-Nagel Polygram Sil G/UV254; detection by
UV light or with phosphomolybdic acid.
The enantiomer excess of the products was determined by GC (Lipodex E and g-Dex columns) or by
HPLC (Chiracel OD H; Chiracel OB H; Chiracel AD; Chiracel AS, or Chiracel OJ columns); tR in min. Optical
rotations: Perkin-Elmer 241 polarimeter; 10-cm quartz cells. IR Spectra: Mattson Instruments Polaris FT-IR
instrument, NaCl cells, in cm 1. NMR Spectra: Varian-XL-200 (1H at 200 MHz, 13C at 50 MHz); Bruker AMX-
400 (1H at 400 MHz, 13C at 100 MHz), and Bruker AMX-500 (1H at 500, 13C at 125 MHz), chemical shifts d in
ppm with respect to SiMe4 (ˆ0 ppm), coupling constants in Hz. MS: Varian CH4 or SM1 spectrometer with
electron impact or electrospray; m/z (rel. %). High-resolution (HR) MS: VG-7070 analytical spectrometer
(data system 11250, resolution 7000).
Aziridines. The aziridines were synthesized by Cu-catalyzed aziridination of the appropriate olefins with
TsNˆIPh [47] as described in the literature. For anal. data of 1, 28, and 35, see [48], for 24, see [49], for 26, see
[50], for 33, see [51].
Catalysts and/or Ligands. The following catalysts and ligands were synthesized according to literature
procedures: 4 [41b], 5 [52], 6 [53], 7 [54], 8 [55], 9a [56] (free ligand), 9b [57][58], 10 [59] (free ligand), 11 and
12: [41c], 13 [22], and 14 [60] (free ligand).
The catalysts 9a, 10, and 14 were prepared by reaction of the free ligands with [CuCl2] in MeOH [54].
{{2,2'-{[(1S,2S)-Cyclohexane-1,2-diyl]bis[(nitrilo-kN)methylidyne]}bis[phenolato-kO]}(2 )}copper (9a):
20
‡
[a]
ˆ
351 (c ˆ 0.008, CHCl3). MS (electrospray): 384.2 (M ).
578
{{2,2'-{[(1S,2S)-Cyclohexane-1,2-diyl]bis[(nitrilo-kN)methylidyne]}bis[4,6-di(tert-butyl)phenolato-
20
‡
kO]}(2 )}copper (9b): [a]
ˆ
260 (c ˆ 0.01, CHCl3). MS (electrospray): 608.6 (M ).
578
{{2,2'-{[(1S,2S')-1,2-Diphenylethane-1,2-diyl]bis[(nitrilo-kN]methylidyne]}bis[phenolato-kO]}(2 )}cop-
20
‡
per (10): [a] ˆ ‡212.5 (c ˆ 0.016, CHCl3). MS (electrospray): 482.14 (M ).
578
{2,2'{[(1S)-[1,1'-Binaphthalene]-2,2'-diyl]bis[(nitrilo-kN)methylidyne]}bis[4,6-di(tert-butyl)phenolato-
21
‡
kO](2 )}copper (14): [a]
ˆ
228.5 (c ˆ 0.028 (CHCl3). MS: 778.6 (M ).
578
[(R)-(1,1'-Binaphthalene-2,2'-diyl] 1-[(4S)-4,5-Dihydro-4-isopropyloxazol-2-yl]-1-methylethyl Phosphite
(ˆ(4S)-2-{1-{[(11bR)-Dinaphtho[2,1-d :1',2'-f][1,3,2]dioxophosphepin-5-yl]oxy}-1-methylethyl}-4,5-dihydro-4-
isopropyloxazole; 16). (4S)-4,5-Dihydro-4-isopropyl-9a-dimethyloxazole-2-methanol (19). For 28 h, 2-hydroxy-
2-methylpropanoic acid (3.0 g, 29 mmol) and l-valinol (3.0 g, 29 mmol) were heated to reflux in p-xylene
(90 ml), and H2O was separated by means of a Dean-Stark trap. After evaporation, the residue was purified by
FC (pentane/AcOEt 1 :1): 19 (1.10 g, 22%). Pale yellow oil. [a]D21
ˆ
100.5 (c ˆ 0.50, CHCl3). IR: 3390m, 1661s,
1
1559m, 1299m, 1180w, 990m, 868m, 789m. H-NMR (400 MHz, CDCl3): 0.88 (d, J ˆ 7.3, 6 H); 0.95 (d, J ˆ 6.8,
6 H); 1.44 (s, 6 H); 1.73 ± 1.82 (m, 1 H); 3.64 (br. s, 1 H); 3.95 (ddd, J ˆ 9.6, 7.6, 5.8, 1 H); 4.10 (dd, J ˆ 7.6, 7.6,
1 H); 4.33 (dd, J ˆ 9.6, 8.3, 1 H). 13C-NMR (100 MHz): 17.7 (q); 18.4 (q); 27.7 (q); 27.9 (q); 32.3 (d); 713 (t);
134.6 (s); 172.3 (s).
Cyclic Phosphite 16. (1R)-[1,1'-binaphthalene]-2,2'-diol (1.0 g, 3.5 mmol) in toluene (20 ml) was added at
788 to PCl3 (0.30 ml, 3.5 mmol) and Et3N (1.0 ml, 7 mmol). After stirring at r.t. for 24 h, the precipitate
(Et3NHCl) was filtered off, and the filtrate was added to Et3N (2.6 g, 25.7 mmol) in toluene (20 ml) at 788.
After stirring for 5 min at 788, 19 (0.60 g, 3.2 mmol) in toluene (5.0 ml) was added to the in situ prepared 18
[23]. The temp. was raised to 258 and the mixture stirred for 12 h. The soln. was filtered, the filtrate evaporated,

672
Helvetica Chimica Acta ± Vol. 84 (2001)
and the residue purified by FC (silica gel, petroleum ether/AcOEt 7:1): 16 (355 mg, 24%). Amorphous solid.
[a]2D3
ˆ
278 (c ˆ 3.0, CHCl3). IR (CHCl3): 3618w, 3020s, 2399m, 1522s, 1420w, 1222s, 1045s, 928s, 799s, 708s,
1
672s. H-NMR (500 MHz, CDCl3): 0.91 (d, J ˆ 7, 3 H); 1.00 (d, J ˆ 6.7, 3 H); 1.67 (s, 3 H); 1.74 (s, 3 H); 1.78 ±
1.88 (m, 1 H); 4.02 (ddd, J ˆ 9.5, 7.5, 6.3, 1 H); 4.12 (dd, J ˆ 6.8, 1.3, 1 H); 4.35 (dd, J ˆ 8.2, 1.2, 1 H); 7.20 ± 7.27
(m, 2 H); 7.36 ± 7.44 (m, 6 H); 7.49 (d, J ˆ 8.8, 1 H); 7.86 ± 7.92 (m, 2 H); 7.94 (d, J ˆ 8.8, 1 H). 13C-NMR
(125 MHz): 17.9 (q); 18.7 (q); 28.0 (d, J ˆ 6.6, q); 32.5 (d); 70.8 (t); 72.1 (d), 75.6 (d, J ˆ 10.7, s); 121.9 (d); 122.4
(d); 123.0 (d, J ˆ 2.5, s); 124.3 (d, J ˆ 5, s); 124.6 (d); 124.8 (d); 125.8 (d); 126.0 (d); 126.9 (d); 127.0 (d); 128.1
(d); 128.2 (d); 129.3 (d); 130.0 (d); 131.1 (s); 131.4 (s); 132.6 (s); 132.7 (d, J ˆ 1.7, s); 147.8 (d, J ˆ 2.5, s); 147.9
(d, J ˆ 4.1, d); 168.1 (s). 31P-NMR (202 MHz, CDCl3): 152.9. MS: 487 (5), 486 (25), 485 (75, M ), 374 (34), 349
‡
(10), 333 (25), 332 (100), 331 (42), 330 (25), 269 (11), 268 (80), 267 (12), 239 (20), 154 (40), 69 (22). HR-MS:
.
‡
485.1765 (C29H28NO4P ; calc. 485.1756).
(‡)-(9S)-9,9'-Biphenanthrene-10,10'-diyl Diisopropylphosphoramidite (ˆ(15bS)-N,N-Diisopropyldiphe-
nanthro[9,10-d :9',10'-f][1,3,2]dioxaphosphepin-4-amine; 17). Diisopropylphosphoramidous dichloride [27]
(21; 79 mg, 0.39 mmol) was added, at 408, to ( )-(9S)-9,9'-biphenanthrene-10,10'-diol ((S)-20) (150 mg,
0.39 mmol) and Et3N (0.11 ml, 0.78 mmol) in toluene (10 ml). The mixture was stirred for 2.5 h at r.t. The
solvent was evaporated, and the residue was purified by FC (silica gel, petroleum ether/AcOEt 3 :1): 17 (113 mg,
57%). Colorless solid. M.p. 206 ± 2088. [a]2D0 ˆ ‡562.5 (c ˆ 0.11, CHCl3). IR (CHCl3): 3619m, 3458(br.), 3024s,
2399m, 1522s, 1391m, 1205s, 1045s, 928m, 799s, 666s. 1H-NMR (200 MHz, CDCl3): 1.12 ± 1.23 (m, 12 H); 3.26 ±
3.52 (m, 2 H); 7.21 ± 7.48 (m, 4 H); 7.51 ± 7.63 (m, 2 H); 7.65 ± 7.83 (m, 4 H); 8.42 (dd, J ˆ 7.6, 1.7, 2 H); 8.53
(dd, J ˆ 7.8, 1.0, 4 H). 13C-NMR (50 MHz): 22.3 (q); 22.6 (q); 45.1 (d); 45.2 (d); 119.0 (s); 120.9 (s), 122.5 (d);
122.7 (d); 122.8 (d); 122.9 (d); 124.3 (d); 124.9 (d); 125.2 (d); 126.1 (d); 126.18 (d); 126.21 (d); 126.5 (d); 127.1
(d); 127.3 (d); 127.4 (d); 127.5 (s); 127.6 (d); 127.8 (s); 127.9 (s); 128.0 (d); 128.3 (s); 131.3 (s); 131.5 (s), 131.7 (s);
‡
146.5 (s); 147.2 (s); 147.3 (s). 31P-NMR (162 MHz, CDCl3): 155.5. MS: 517 (8), 516 (16), 515 (96, M ), 501 (31),
500 (37), 472 (23), 459 (18), 457 (51), 417 (16), 416 (65), 415 (86), 376 (10), 369 (32), 368 (100), 353 (23), 352
.
‡
(62), 339 (28), 88 (15), 86 (15), 46 (77). HR-MS: 515.2003 (C34H30NO2P ; calc. 515.2014). Anal. calc. for
C34H30NO2P: C 79.26, H 5.86, N 2.71; found: C 79.26, H 6.12, N 2.51.
Cu-Catalyzed Opening of 1 with Grignard Reagents: General Procedures. Method A. To the appropriate Cu
complex (0.04 mmol) and 1 (0.4 mmol) in THF (2.0 ml), the Grignard reagent (0.48 mmol) in Et2O (0.5 ml) was
added dropwise at 08. After the addition, the mixture was stirred at 08 for the time indicated and then
hydrolyzed with sat. NH4Cl soln. (10 ml) and extracted with Et2O (3 Â 10 ml). The extract was washed with sat.
NaCl soln. (10 ml), dried (MgSO4), and evaporated, and the products were purified by FC.
Method B. A soln. of [Cu(OTf)2] (14.4 mg, 0.04 mmol) and the appropriate ligand were stirred in THF
(2.0 ml) for 1 h at r.t. After addition of 1 (100 mg, 0.40 mmol), the mixture was cooled to 08, and the Grignard
reagent (0.40 mmol) in Et2O (0.12 ml) was added dropwise. The mixture was stirred at 08 for the time indicated
and then hydrolyzed with sat. NH4Cl soln. The aq. layer was extracted with Et2O (10 ml), the combined org.
layer washed with sat. NaCl soln., dried (MgSO4), and evaporated, and the crude product purified by FC.
N-(trans-2-Azidocyclohexyl)-4-methylbenzenesulfonamide (2a) [19]: M.p. 69 ± 718. IR (CHCl3): 3310s,
2965vs, 2469w, 2016vs, 1469s. 1H-NMR (400 CDCl3): 1.21 ± 1.26 (m, 3 H); 1.60 ± 1.72 (m, 2 H); 2.01 ± 2.09
(m, 2 H); 2.43 (s, 3 H); 2.92 ± 2.94 (m, 1 H); 3.04 ± 3.09 (m, 2 H); 4.75 (m, J ˆ 5.9, 1 H); 7.31 (d, J ˆ 8, 2 H); 7.79
(d, J ˆ 8, 2 H). 13C-NMR (100 MHz): 21.5 (q); 23.7 (t); 30.1 (t); 30.8 (t); 32.5 (t); 56.7 (d); 63.6 (d); 127.1 (d);
129.6 (d); 137.5 (s); 143.5 (s). MS: 249 (1), 210 (19), 155 (38), 111 (38), 94 (22), 92 (14), 91 (100), 84 (17), 65
(22), 56 (38).
N-(trans-2-Chlorocyclohexyl)-4-methylbenzenesulfonamide (2b): M.p. 100 ± 1028 ([61]: 100 ± 1028). IR
(CHCl3): 3378w, 3024s, 2945w, 1599w, 1450w, 1413w, 1335m, 1101s, 765s. 1H-NMR (400 MHz, CDCl3): 1.15 ± 1.39
(m, 4 H); 1.51 ± 1.81 (m, 4 H); 2.10 ± 2.38 (m, 2 H); 2.42 (s, 3 H); 2.99 ± 3.18 (m, 1 H); 3.61 ± 3.81 (m, 1 H); 4.82
(d, J ˆ 5.3, 1 H); 7.76 (d, J ˆ 8.2, 2 H); 7.31 (d, J ˆ 8.2, 2 H). 13C-NMR (100 MHz): 33.5 (t); 35.5 (t); 38.6 (t); 62.3
‡
‡
(d); 64.5 (d); 127.7 (d); 129.2 (d); 138.1 (s); 143.9 (s). MS: 289 (11, M ), 287 (31, M ), 252 (14), 211 (12), 210
(100), 155 (77), 132 (21), 96 (15), 91 (98), 65 (19).
N-(trans-2-Bromocyclohexyl)-4-methylbenzenesulfonamide (2c): Colorless crystals. M.p. 104 ± 1068 ([21]:
1
105 ± 1078). IR (CHCl3): 3378w, 3024s, 2943s, 1599w, 1332s. H-NMR (400 MHz, CDCl3): 1.19 ± 1.33 (m, 3 H);
1.36 ± 1.40 (m, 1 H); 1.69 ± 1.72 (m, 1 H); 1.92 ± 2.01 (m, 1 H); 2.27 ± 2.39 (m, 2 H); 2.43 (s, 3 H); 3.21 ± 3.26
(m, 1 H); 3.94 ± 3.99 (m, 1 H); 4.78 (d, J ˆ 5.6, 1 H); 7.32 (d, J ˆ 8, 2 H); 7.79 (d, J ˆ 8, 2 H). 13C-NMR
(100 MHz): 33.4 (t); 34.9 (d); 38.1 (t); 59.3 (d); 63.5 (d); 127.5 (d); 129.6 (d); 137.1 (s); 143.6 (s). MS: 333 (23,
‡
M ), 252 (16), 210 (97), 155 (82), 96 (62), 91 (100), 69 (21).
4-Methyl-N-(trans-2-methylcyclohexyl)benzenesulfonamide (3a): Colorless solid. M.p. 98 ± 1008. IR
(CHCl3): 2929vs, 2857s, 1448w, 1415w, 1328s, 1157s. 1H-NMR (400 MHz, CDCl3): 0.81 (d, J ˆ 6.8, 3 H);

Helvetica Chimica Acta ± Vol. 84 (2001)
673
1.08 ± 1.25 (m, 5 H); 1.57 ± 1.58 (m, 2 H); 1.70 ± 1.72 (m, 2 H); 2.41 (s, 3 H); 2.64 ± 2.65 (m, 1 H); 4.70 ± 4.80
(m, 1 H); 7.27 (d, J ˆ 8, 2 H); 7.76 (d, J ˆ 8, 2 H). 13C-NMR (100 MHz): 19.1 (q); 21.5 (q); 25.3 (t); 34.5 (t); 38.3
‡
(d); 59.1 (d); 60.3 (s); 126.9 (d); 129.5 (d); 138.7 (s); 142.9 (s). MS: 267 (66, M ), 210 (100), 155 (94), 91 (95), 65
.
‡
(20). HR-MS: 267.1280 (C14H21NO2S ; calc. 267.12930). Anal. calc. for C14H21NO2S: C 62.87, H 7.92, N 5.27;
found: C 62.70, H 7.86, N 5.27.
Enantiomer separation of 3a: HPLC (Chiracel OD H, hexane/iPrOH 9 :1, 0.5 ml/min): tR 13.4 ((1S,2S)-3a),
14.5 ((1R,2R)-3a).
Absolute Configuration of 3a. To the sulfonamide 3a (100 mg, 1.50 mmol; obtained from 1 and MeMgBr in
the presence of catalyst 8) in liq. NH3 (20 ml), Na (172 mg, 7.50 mmol) was added in small portions at 788. The
mixture was stirred at 788 for 2 h, whereupon an excess of NH4Cl was added until the blue color disappeared.
The solvent was evaporated slowly. The residue was dissolved in AcOEt (25 ml) and 2m HCl (25 ml). The aq.
layer was washed with AcOEt (2 Â 25 ml), then made basic with NH4OH, and extracted with AcOEt (3 Â
25 ml). The org. phase was dried (Na2SO4) and evaporated. The crude product was dissolved in Et2O (20 ml)
and precipitated with HCl gas. The precipitate was filtered, dissolved in 1m NaOH, and extracted with Et2O to
afford trans-2-methylcyclohexanamine (22) (104 mg, 61%). Transparent oil. [a]2D0 ˆ ‡20.2 (c ˆ 10.0, Et2O) for
55% ee ([62]: [a]1D9 ˆ ‡30.8 for (1S,2S)-22). B.p. 140 ± 1428. IR (CHCl3): 2927s, 2871m, 2361w, 1748s, 1597w,
1575w, 1456m, 1369m, 1257s, 1096w, 955m, 803s, 734s. 1H-NMR (400 MHz, CDCl3): 0.97 (d, J ˆ 6.3, 3 H); 1.10 ±
1.13 (m, 3 H); 1.55 ± 1.80 (m, 4 H); 1.90 ± 2.10 (m, 2 H); 2.28 (dt, J ˆ 10.5, 4.5, 1 H); 3.60 (br. s, 2 H). 13C-NMR
(100 MHz): 19.1 (q); 25.8 (t); 26.2 (t); 34.2 (t); 36.3 (t); 40.8 (d); 56.7 (d).
4-Methyl-N-(trans-2-pentylcyclohexyl)benzenesulfonamide (3b): FC (pentane/AcOEt 15 :1). Colorless
1
solid. M.p. 55 ± 588. IR (CHCl3): 3009w, 2930s, 2857w, 1448w, 1325w, 1221s, 1157s, 1091w, 799s, 769s. H-NMR
(400 MHz, CDCl3): 0.86 (t, J ˆ 7.2, 3 H); 0.84 ± 1.82 (m, 17 H); 2.43 (s, 3 H); 2.85 (ddd, J ˆ 10.1, 10.1, 4, 1 H);
4.29 (d, J ˆ 8.9, 1 H); 7.30 (d, J ˆ 8, 2 H); 7.83 (d, J ˆ 8, 2 H). 13C-NMR (125 MHz): 14.5 (q); 19.8 (t); 22.0 (q);
22.9 (t); 23.2 (t), 25.5 (t); 26.4 (t); 31.2 (t); 32.5 (d); 40.2 (t); 43.5 (d); 57.8 (d); 127.4 (d); 131.3 (d); 139.0 (s); 143.4
‡
(s). MS: 323 (32, M ), 280 (10), 266 (12), 210 (50), 172 (17), 168 (58), 155 (49), 152 (20), 96 (56), 95 (13), 92
‡
(12), 91 (100), 82 (14), 69 (23), 67 (17), 65 (19), 56 (16), 55 (21). HR-MS: 323.1869 (C18H29O2NS ; calc.
323.1910).
Enantiomer separation of 3b: HPLC (ODH, hexane/iPrOH 9 :1, 0.5 ml/min): tR 10.0, 11.2.
N-(trans-2-Isopropylcyclohexyl)-4-methylbenzenesulfonamide (3c): FC (pentane/AcOEt 6 :1). Colorless
1
solid. M.p. 88 ± 918. IR (CHCl3): 2937m, 2859w, 1599w, 1156s, 1092w, 766s. H-NMR (500 MHz, CDCl3): 0.46
(d, J ˆ 6.7, 3 H); 0.76 (d, J ˆ 6.7, 3 H); 0.85 ± 1.22 (m, 4 H); 1.29 ± 1.38 (m, 1 H); 1.48 ± 1.60 (m, 2 H); 1.63 ± 1.77
(m, 2 H); 1.96 (dsept., J ˆ 4.5, 2.8, 1 H); 2.35 (s, 3 H); 2.89 ± 2.98 (m, 1 H); 4.19 (d, J ˆ 8.9, 1 H); 7.21 (d, J ˆ 8,
2 H); 7.69 (d, J ˆ 8, 2 H). 13C-NMR (125 MHz): 15.5 (q); 21.1 (q); 22.8 (t); 25.2 (t); 25.9 (d); 35.1 (t); 48.8 (d);
‡
54.7 (d); 126.9 (d); 129.5 (d); 137.7 (s); 142.0 (s). MS: 295 (2, M ), 155 (14), 140 (17), 124 (11), 96 (100), 91 (35),
‡
69 (42), 65 (12), 55 (11). HR-MS: 295.1605 (C16H25NO2S , calc. 295.1606).
Enantiomer separation of 3c: HPLC (ODH, hexane/iPrOH 9 :1, 0.5 ml/min): tR 15.3, 16.5.
4-Methyl-N-(trans-2-phenylcyclohexyl)benzenesulfonamide (3d). FC (hexane/AcOEt 9 :1). Colorless
crystals. M.p. 146 ± 1488. [a]D21
ˆ
5.89 (c ˆ 2.01, CHCl3) for 53% ee. IR (CHCl3): 3027m, 2936m, 2859w,
1599w, 1493w, 1449w, 1405w, 1335w, 1228m, 1160s, 1093w, 1073w, 897w. 1H-NMR (400 MHz, CDCl3): 1.20 ± 1.45
(m, 5 H); 1.68 ± 1.85 (m, 3 H); 2.33 (ddd, J ˆ 11.3, 11.0, 3.4, 1 H); 2.42 (s, 3 H); 3.02 ± 3.15 (m, 1 H); 4.18 (d, J ˆ
4.4, 1 H); 6.84 (d, J ˆ 6.9, 2 H); 7.0 ± 7.18 (m, 5 H); 7.32 (d, J ˆ 8.4, 2 H). 13C-NMR (100 MHz): 21.5 (q); 25.0 (t);
25.8 (t); 34.7 (t); 35.0 (t); 50.4 (d); 57.4 (d); 126.8 (d); 127.0 (d); 128.8 (d); 129.4 (d); 136.9 (s); 142.1 (s); 142.7
‡
(s). MS: 329 (3, M ), 210 (14), 174 (55), 159 (14), 158 (100), 157 (17), 155 (27), 129 (11), 115 (13), 96 (14), 91
.
‡
(90), 65 (14). HR-MS: 329.1418 (C19H23NO2S ; calc. 329.1449).
Enantiomer separation of 3d: HPLC (Chiracel AD, hexane/iPrOH 25 :1, 0.5 ml/min): tR 35.4 ((1S,2R)-3d),
42.3 ((1R,2S)-3d).
Absolute Configuration of 3d. A soln. of TsCl (648 mg, 3.40 mmol) in CH2Cl2 (5.0 ml) was added dropwise
to enantiomerically enriched (‡)-(1S,2R)-trans-2-phenylcyclohexanamine (1S,2R-23) (53% ee; 585 mg,
3.36 mmol) [63] and Et3N (0.94 ml, 6.7 mmol) in CH2Cl2 (10 ml). The mixture was stirred at r.t. for 2 h,
whereupon H2O (20 ml) was added. After extraction with CH2Cl2 (3 Â 20 ml), the org. phase was washed with
sat. NaCl soln. and dried (MgSO4): 46% of (1S,2R)-3d. [a]2D0 ˆ ‡12 (c ˆ 1.84, CHCl3) for 53% ee.
4-Methyl-N-[trans-2-(2,4,6-trimethylphenyl)cyclohexyl]benzenesulfonamide (3e): FC (hexane/AcOEt
9 :1). Colorless crystals. M.p. 143 ± 1468. IR (CHCl3): 3315w, 2938m, 2858w, 1450w, 1401w, 1317w, 1226s,
1212m, 1159m, 1093w, 1063w, 908w, 854w, 733w, 716m. 1H-NMR (400 MHz, CDCl3): 1.21 ± 1.48 (m, 5 H); 1.60 ±
1.88 (m, 6 H); 1.93 (s, 3 H); 2.24 (s, 3 H); 2.30 (s, 3 H); 2.44 (s, 3 H); 2.93 (ddd, J ˆ 10.8, 10.8, 3.7, 1 H); 3.56 ±
3.63 (m, 1 H); 4.09 (s, J ˆ 4, 1 H); 6.54 (s, 1 H); 6.81 (s, 1 H); 7.16 (d, J ˆ 8, 2 H); 7.41 (d, J ˆ 8, 2 H). 13C-NMR

674
Helvetica Chimica Acta ± Vol. 84 (2001)
(100 MHz): 19.3 (t); 20.6 (q); 20.9 (q); 21.4 (q); 21.9 (q); 22.7 (t); 24.9 (t); 26.4 (t); 29.8 (t); 35.5 (t); 45.5 (d); 54.6
(d); 126.9 (d); 129.2 (d); 129.5 (d); 131.6 (d); 133.8 (s); 135.9 (s); 136.0 (s); 136.9 (s); 137.3 (s); 142.7 (s). MS: 372
‡
(11), 371 (43, M ), 217 (16), 216 (100), 199 (14), 154 (14), 133 (59), 96 (22), 91 (37), 56 (15). HR-MS: 371.1938
.
‡
(C22H29NO2S ; calc. 371.1919).
Enantiomer separation of 3e: HPLC (Chiracel OD H, 0.5 ml/min): tR 17.1, 24.8.
4-Methyl-N-(trans-6-methylcyclohex-3-enyl)benzenesulfonamide (25): FC (hexane/AcOEt 9 :1). M.p. 79 ±
8818. IR (CHCl3): 3542w, 3382m, 3272w, 3028s, 2924m, 2837w, 2359w, 1599m, 1415m, 1227s, 1158s, 1094m, 953w,
814m. 1H-NMR (400 MHz, CDCl3): 0.88 (d, J ˆ 6.4, 3 H); 1.65 ± 1.90 (m, 3 H); 2.14 ± 2.25 (m, 2 H); 2.48
(s, 3 H); 3.11 ± 3.20 (m, 1 H); 4.64 (d, J ˆ 8.8, 1 H); 5.40 ± 5.48 (m, 1 H); 5.54 ± 5.61 (m, 1 H); 7.29 (d, J ˆ 8.4,
2 H); 7.76 (d, J ˆ 8.4, 2 H). 13C-NMR (100 MHz): 18.3 (q); 21.5 (q); 31.8 (t); 32.9 (d); 54.4 (d); 123.8 (d); 126.3
‡
(d); 127.0 (d); 129.6 (d); 138.6 (s); 143.1 (s). MS: 265 (6, M ), 213 (6), 212 (12), 211 (100), 155 (45), 147 (22),
139 (87), 120 (15), 110 (12), 94 (86), 92 (13), 91 (95), 79 (12), 67 (12), 65 (20), 56 (36), 55 (10). HR-MS:
.
‡
265.1178 (C14H19NOS ; calc. 265.1136).
Enantiomer separation of 25: HPLC (Chiracel OD H, hexane/iPrOH 9 :1, 0.5 ml/min): tR 14.1, 16.0.
4-Methyl-N-(trans-2-methylcyclopentyl)benzenesulfonamide (27): FC (hexane/AcOEt 9 :1). Colorless oil.
IR (CHCl3): 2960w, 2872w, 1457w, 1418w, 1328m, 1158s, 1093m, 910w. 1H-NMR (400 MHz, CDCl3): 0.90 (d, J ˆ
6.4, 3 H); 1.05 ± 1.15 (m, 1 H); 1.20 ± 1.30 (m, 1 H); 1.45 ± 1.70 (m, 4 H); 1.75 ± 1.90 (m, 1 H); 2.43 (s, 3 H); 3.00 ±
3.10 (m, 1 H); 4.39 (d, J ˆ 7.9, 1 H); 7.30 (d, J ˆ 8, 2 H); 7.76 (d, J ˆ 8.4, 2 H). 13C-NMR (100 MHz): 17.6 (q); 21.4
(q); 21.6 (t); 31.6 (t); 32.9 (t); 41.2 (d); 61.7 (d); 127.1 (d); 129.6 (d); 135.0 (d); 138.1 (d); 143.1 (s); 143.2 (s). MS:
‡
253 (45, M ), 224 (15), 211 (13), 210 (98), 155 (71), 98 (50), 92 (17), 91 (100), 82 (24), 65 (24), 56 (12), 55 (15).
.
‡
HR-MS: 253.1139 (C13H19NOS ; calc. 253.1136).
Enantiomer separation of 27: HPLC (Chiracel OB,H, hexane/iPrOH 9 :1, 0.4 ml/min): tR 26.4, 29.4.
Rearrangement of Aziridines to Allylic Amines. General Procedure. ( )-Sparteine (340 mg, 1.45 mmol) in
s
Et2O (1.0 ml) was added within 10 min at 788 to BuLi in Et2O (3.0 ml). After stirring for 1 h at 788, the
aziridine (0.50 mmol) was added, and the mixture was stirred for 4 h at 788. It was warmed to r.t., and sat.
NH4Cl soln. was added. The mixture was extracted with Et2O (3 Â 10 ml), the org. layer dried (Na2SO4) and
evaporated, and the crude product purified by FC.
Rearrangement of 1. FC (pentane/AcOEt 4 :1) gave N-(cyclohex-2-en-1-yl)-4-methylbenzenesulfonamide
(31; 35%) and N-(cyclohex-1-en-1-yl)-4-methylbenzenesulfonamide (32; 31%).
Data of 31 [64]: Colorless solid. M.p. 104 ± 1068 ([65]: 108 ± 1098). [a]2D1 ˆ ‡19.8 (c ˆ 1.50, CHCl3) for 39%
ee. IR (CHCl3): 3541w, 3389m, 3272w, 3024s, 2926m, 2817w, 2364w, 1599m, 1411m, 1231s, 1157s, 1094m, 978w,
811m. 1H-NMR (500 MHz, CDCl3): 1.49 ± 1.69 (m, 3 H); 1.71 ± 1.79 (m, 1 H); 1.82 ± 2.01 (m, 2 H); 2.43 (s, 3 H);
3.78 ± 3.85 (m, 1 H); 4.58 (d, J ˆ 8.5, 1 H); 5.32 ± 5.38 (m, 1 H); 5.74 ± 5.79 (m, 1 H); 7.31 (d, J ˆ 8.2, 2 H); 7.78
(d, J ˆ 8.2, 2 H). 13C-NMR (125 MHz): 19.2 (t); 21.5 (q); 24.4 (t); 30.2 (t); 48.9 (d); 126.9 (d); 127.0 (d); 129.6
(d); 131.5 (d); 138.3 (s); 143.2 (s).
Enantiomer separation of 31. HPLC (Chiracel AS, hexane/iPrOH 9 :1, 0.5 ml/min): tR 26, 29.
Data of 32 [65]: Semi-solid. IR (CHCl3): 3555w, 3361m, 3282w, 3017s, 2847w, 2361w, 1603m, 1413m, 1214s,
1163s, 1084m, 943w. 1H-NMR (500 MHz, CDCl3): 1.22 ± 1.31 (m, 2 H); 1.42 ± 1.58 (m, 2 H); 1.62 ± 1.81 (m, 2 H);
1.87 ± 1.93 (m, 1 H); 2.11 ± 2.18 (m, 1 H); 2.46 (s, 3 H); 4.22 ± 4.27 (m, 1 H); 4.54 (d, J ˆ 4.5, 1 H); 7.33 (d, J ˆ 7.8,
2 H); 7.69 (d, J ˆ 7.8, 2 H). 13C-NMR (125 MHz): 20.4 (q); 21.5 (q); 24.9 (t); 27.2 (t); 32.7 (t); 50.0 (d); 127.1 (d);
129.6 (d); 131.7 (s); 143.7 (s).
4-Methyl-N-[rel-(1R,3aS,6aS)-octahydropentalen-1-yl]benzenesulfonamide (34). FC (SiO2, pentane/AcOEt
4 :1). Yield 71%. Colorless solid. M.p. 106 ± 1088. [a]2D1 ˆ ‡29.1 (c ˆ 0.975, CHCl3) for 75% ee. IR (CHCl3):
3385w, 3021s, 2951s, 2361w, 1600w, 1452w, 1341m, 1156s, 1092s, 926w, 761w. 1H-NMR (500 MHz, CDCl3): 1.00 ±
1.11 (m, 1 H); 1.12 ± 1.39 (m, 4 H); 1.42 ± 1.71 (m, 4 H); 1.82 ± 1.93 (m, 1 H); 2.29 ± 2.38 (m, 2 H); 2.45 (s, 3 H);
3.51 ± 3.62 (m, 1 H); 4.62 (d, J ˆ 7.4 (1 H); 7.32 (d, J ˆ 8.3, 2 H); 7.79 (d, J ˆ 8.3, 2 H). 13C-NMR (125 MHz): 21.4
(q); 27.2 (t); 27.9 (t); 29.3 (t); 30.5 (t); 35.4 (t); 41.2 (d); 45.4 (d); 57.0 (d); 127.0 (d); 129.5 (d); 137.9 (s). MS: 279
‡
(23, M ), 250 (15), 211 (13), 210 (100), 184 (17), 155 (62), 124 (68), 108 (21), 107 (15), 92 (16), 91 (88), 79 (15),
.
‡
67 (14), 65 (19), 56 (15), 55 (18). HR-MS: 279.1287 (C15H21O2NS ; calc. 279.1293).
Enantiomer separation of 34: HPLC (Chiracel OD H, hexane/iPrOH 25 :1, 0.5 ml/min): tR 27, 29.
4-Methyl-N-(tricyclo[2.2.1.02,6]hept-3-yl)benzenesulfonamide (36). Reaction in pentane. FC (pentane/
AcOEt 4 :1). Yield 72%. Colorless solid. M.p. 121 ± 1228. [a]D21
ˆ
0.7 (c ˆ 1.04, CHCl3) for 43% ee. IR
(CHCl3): 3388w, 3035w, 2875w, 1600w, 1418w, 1339m, 1292w, 1231s, 1159s, 1987m, 910w, 813m. 1H-NMR
(500 MHz, CDCl3): 0.85 ± 0.90 (m, 1 H); 1.05 ± 1.12 (m, 2 H); 1.16 (d, J ˆ 10.7, 2 H); 1.26 (d, J ˆ 10.7, 2 H); 1.49
(t, J ˆ 10.7, 1 H); 1.76 (s, 1 H); 2.39 (s, 3 H); 3.18 (d, J ˆ 7.25, 1 H); 4.73 (d, J ˆ 2.25, 1 H); 7.27 (d, J ˆ 7.8, 2 H);
7.75 (d, J ˆ 7.8, 2 H). 13C-NMR (125 MHz): 10.3 (q); 11.9 (d); 14.6 (d); 21.5 (d); 29.3 (t); 31.3 (q); 34.0 (q); 58.9

Helvetica Chimica Acta ± Vol. 84 (2001)
675
‡
(d); 127.0 (d); 129.6 (d); 138.0 (s); 143.1 (s). MS: 263 (7, M ), 108 (84), 106 (15), 93 (17), 92 (100), 91 (79), 81
.
‡
(22), 80 (14), 79 (11), 77 (10), 67 (11), 65 (18). HR-MS: 263.0972 (C14H17O2NS ; calc. 263.0980).
Enantiomer separation of 36: HPLC (Chiracel OD H, hexane/iPrOH 9 :1, 0.5 ml/min): tR 15.3 ((S)-36),
16.3 (R)-36).
Absolute Configuration of 36. Partial Resolution of 37: (‡)-(R)-a-methylbenzylamine (1.66 g, 13.8 mmol)
was added dropwise to racemic tricyclo[2.2.1.02,6]heptane-3-carboxylic acid (37) [36][37] (1.90 g, 13.8 mmol) in
Et2O (40 ml). A precipitate formed immediately. The mixture was stirred for 1.5 h and then evaporated. The
recovered crude salt (3.44 g) was dissolved in refluxing acetone (30 ml), to which hot hexane (30 ml) was added
slowly. The soln. was cooled, whereupon crystallization started. After 3 recrystallizations, 650 mg of salt was
obtained having [a]D21 ˆ ‡24.3 (c ˆ 0.82, CHCl3). The salt was dissolved in 20% HCl soln. (10 ml), to which solid
NaCl (500 mg) was added. The soln. was extracted with AcOEt (5 Â 20 ml), the org. layer washed (sat. NaCl
soln.), dried, and evaporated to yield enantiomer-enriched acid (R)-37 (323 mg, 17%). [a]2D1 ˆ ‡12.3 (c ˆ 2.0,
EtOH) for 53% ee, determined on (R)-36).
Curtius Degradation of (R)-37. (3R)-Tricyclo[2.2.1.02,6]heptan-3-amine ((R)-38). To the enantiomer-
enriched (R)-37 (prepared above; 300 mg, 2.21 mmol) in toluene (20 ml), Et3N (1.21 ml) and diphenylphos-
phoryl azide (1.19 g) were added at 08. The mixture was stirred for 40 min at r.t., and H2O (10 ml) was added.
The soln. was concentrated to ca. 50%, the aq. layer extracted with Et2O (4 Â 15 ml), the combined org. phase
dried (MgSO4) and evaporated, and the crude product purified by FC (pentane/AcOEt 9 :1): carbonyl azide
(190 mg, 54%). Yellowish oil. 1H-NMR (500 MHz, CDCl3): 1.23 ± 1.43 (m, 3 H); 1.36 ± 1.45 (m, 3 H); 1.51 ± 1.55
(m, 1 H); 2.24 ± 2.27 (m, 1 H); 2.42 ± 2.44 (m, 1 H). 13C-NMR (125 MHz): 10.3 (d); 11.6 (d), 12.9 (d), 30.6 (t);
33.7 (d); 34.4 (t); 52.0 (d); 181.3 (s).
The azide (180 mg, 1.10 mmol) was refluxed in toluene (10 ml) for 30 min, whereupon 1m HCl (4.0 ml) was
added. Refluxing was continued for 2 h. After cooling, 20% NaOH soln. was added until the pH of the soln.
reached 12. The mixture was extracted with Et2O (4 Â 20 ml) and the extract washed with sat. NaCl soln., dried
(MgSO4), and evaporated: free amine (R)-38. Colorless oil. [a]2D1 ˆ ‡8.2 (c ˆ 1.0, EtOH) for 53% ee,
determined on (R)-36 ([39]: [a]D25
ˆ
67 (neat for (S)-38)). IR (CHCl3) 3334w, 2927s, 2361w, 1597w, 1575w,
1456m, 1369m, 1167s, 1096w, 955m, 814s, 734s. 1H-NMR (500 MHz, CDCl3): 0.97 ± 1.02 (m, 1 H); 1.10 ± 1.25
(m, 4 H); 1.26 ± 1.31 (m, 1 H); 1.37 (d, J ˆ 10.4, 1 H); 1.91 (s, 1 H); 3.48 (m, 3 H); 4.37 (br. s, 1 H). 13C-NMR
(125 MHz): 10.3 (d); 12.1 (d); 14.7 (d); 29.0 (t); 30.7 (t); 34.1 (d); 56.4 (d).
Sulfonamidation of (R)-38. A soln. of TsCl (130 mg, 0.68 mmol) in CH2Cl2 (2.0 ml) was added dropwise to
(R)-38 (70 mg, 0.57 mmol) and Et3N (0.16 ml, 1.14 mmol) in CH2Cl2 (5.0 ml). After 2 h stirring at r.t., H2O
(10 ml) was added, and the mixture was extracted with sat. NaCl soln., dried (MgSO4), and evaporated: (R)-36
(93 mg, 62%). Colorless solid. [a]D21
ˆ
1.01 (c ˆ 0.99, CHCl3) for 53% ee.
REFERENCES
[1] D. Tanner, Angew. Chem., Int. Ed. 1994, 33, 599.
[2] a) P. Müller, in ꢀAdvances in Catalytic Processesꢁ, Ed. M. P. Doyle, JAI Press, Greenwhich, 1997, Vol. 2;
b) E. N. Jacobsen, in ꢀComprehensive Asymmetric Catalysisꢁ, Eds. E. N. Jacobsen, A. Pfaltz, and H.
Yamamoto, Springer, New York, 1999, Chapt. 17; c) C. J. Sanders, K. M. Gillespie, D. Bell, P. Scott, J. Am.
Chem. Soc. 2000, 122, 7132; d) M. J. Södegren, D. A. Alonso, A. V. Bedekar, P. G. Andersson, Tetrahedron
Lett. 1997, 38, 6897; M. J. Södegren, D. A. Alonso, P. G. Andersson, Tetrahedron: Asymmetry 1997, 8, 3563;
d) D. Macikenas, E. Skrzypezak-Jankun, J. D. Protasiewicz, J. Am. Chem. Soc. 1999, 121, 7164.
[3] D. M. Hodgson, A. R. Gibbs, G. P. Lee, Tetrahedron 1996, 46, 14361.
[4] D. M. Hodgson, G. P. Lee, R. E. Marriott, A. J. Thompson, R. Wisedale, J. Witherington, J. Chem. Soc.,
Perkin Trans 1 1998, 2151.
[5] a) J. K. Whitesell, S. W. Felman, J. Org. Chem. 1980, 45, 755; b) H. Su, L. Walder, R. Scheffold, Helv. Chim.
Ã
Acta 1988, 71, 1073; P. Bonhote, R. Scheffold, Helv. Chim. Acta 1991, 74, 1425; c) D. Bhuniya, V. K. Singh,
Synth. Commun. 1994, 24, 375; d) D. Bhuniya, V. K. Singh, Synth. Commun. 1994, 24, 1475; e) M. J.
Södergren, P. G. Andersson, J. Am. Chem. Soc. 1998, 120, 10670; f) M. J. Södergren, S. K. Bertilsson, P. G.
Andersson, J. Am. Chem. Soc. 2000, 122, 6610.
[6] H. C. Brown, N. N. Joshi, M. Strebnik, J. Am. Chem. Soc. 1988, 110, 6246; H. Yamamoto, Y. Naruse, T.
Eraki, Tetrahedron 1988, 44, 4747; H. Yamamoto, T. Mukajyama, Chem. Lett. 1985, 1645.
[7] a) H. Yamashita, Chem. Lett. 1987, 525; b) M. Hayashi, K. Kademura, N. Oguni, Synlett 1991, 774; c) H.
Adolffson, C. Moberg, Tetrahedron: Asymmetry 1995, 6, 2023; d) L. E. Martinez, J. L. Leighton, D. H.

676
Helvetica Chimica Acta ± Vol. 84 (2001)
Carsten, E. N. Jacobsen, J. Am. Chem. Soc. 1996, 118, 5897; e) K. B. Hansen, J. L. Leighton, E. N. Jacobsen,
J. Am. Chem. Soc. 1996, 118, 10924; f) M. L. Snapper, Angew. Chem., Int. Ed. 1996, 35, 1668.
[8] S. Matsubara, T. Kodama, K. Utimoto, Tetrahedron Lett. 1990, 31, 6379; M. Meguro, N. Asao, Y.
Yamamoto, Tetrahedron Lett. 1994, 35, 7395; W.-H. Leung, M.-T. Yu, M.-C. Wu, L.-L. Yeung, Tetrahedron
Lett. 1996, 37, 891; E. K. F. Chow, M.-C. Wu, P. W. Y. Kum, L.-L. Yeung, Tetrahedron Lett. 1995, 36,
107.
[9] Z. Sekar, V. K. Singh, J. Org. Chem. 1999, 64, 2537.
Â
[10] Z. Li, M. Fernandez, E. N. Jacobsen, Org. Lett. 1999, 1, 1611.
[11] M. Hayashi, K. Ono, H. Hoshimi, N. Oguni, J. Chem. Soc., Chem. Commun. 1994, 2699; M. Hayashi, K.
Ono, H. Hoshini, N. Oguni, Tetrahedron 1996, 52, 7817.
[12] M. J. Eis, B. Ganem, Tetrahedron Lett. 1985, 26, 1153.
[13] J. E. Baldwin, R. M. Adlington, I. A. OꢁNeill, C. Schofield, A. C. Spivey, J. B. Sweeney, J. Chem. Soc.,
Chem. Commun. 1989, 1852.
[14] D. Tanner, C. Birgresson, H. K. Dhaliwal, Tetrahedron Lett. 1990, 31, 1903; D. Tanner, T. Groth,
Tetrahedron 1997, 53, 16139; D. Tanner, P. Somfai, Tetrahedron 1988, 44, 619.
[15] H. Aoyama, N. Mimura, H. Ohno, K. Ishii, A. Toda, H. Tamamura, A. Otaka, N. Fujii, T. Ibuka,
Tetrahedron Lett. 1997, 38, 7383; R. S. Atkinson, A. P. Ayscough, W. T. Gattrell, T. M. Raynham,
Tetrahedron Lett. 1998, 39, 497.
[16] A. A. Cantrill, A. N. Jarvis, H. M. I. Osbom, A. Ouadi, J. B. Sweeney, Synlett 1996, 847; A. A. Cantrell, J. B.
Sweeney, Synlett 1995, 1277; H. M. I. Osborn, J. B. Sweeney, Synlett 1994, 145.
[17] P. Müller, C. Baud, Y. Jacquier, M. Moran, I. Nägeli, J. Phys. Org. Chem. 1996, 9, 341; P. Müller, C. Baud, I.
Jacquier, Tetrahedron 1996, 52, 1543; P. Müller, C. Baud, I. Jacquier, Can. J. Chem. 1998, 738.
[18] P. Müller, P. Nury, Org. Lett. 1999, 1, 439.
[19] W.-H. Leung, M.-T. Yu, M.-C. Wu, L.-L. Yeung, Tetrahedron Lett. 1996, 37, 891.
[20] J. F. Larrow, S. E. Schaus, E. N. Jacobsen, J. Am. Chem. Soc. 1996, 118, 7420; S. E. Schaus, J. F. Larrow, E. N.
Jacobsen, J. Org. Chem. 1997, 62, 4197.
[21] D. H. R. Barton, M. R. Britten-Kelly, D. Ferreira, J. Chem. Soc., Perkin Trans. 1 1978, 1090.
[22] P. Müller, P. Nury, Helv. Chim. Acta 2000, 83, 843.
[23] N. Green, T. D. Kee, Synth. Commun. 1993, 23, 1651.
[24] Y. Lin, L.-C. Chien, Tetrahedron: Asymmetry 1998, 9, 63.
[25] M. Noji, M. Nakajima, K. Koga, Tetrahedron Lett. 1994, 35, 7983.
[26] F. Toda, K. Tanaka, J. Org. Chem. 1988, 53, 3607.
[27] S. Han, C. M. Harris, T. M. Harris, H.-Y. Hong Kim, S. J. Kim, J. Org. Chem. 1996, 61, 174.
[28] P. Nury, planned Ph.D. Thesis, University of Geneva.
[29] D. A. Alonso, P. G. Andersson, J. Org. Chem. 1998, 63, 9455.
[30] H. Nohira, K. Ehara, A. Miyashita, Bull. Chem. Soc. Jpn. 1970, 43, 2230.
[31] M. Kawal, T. Iwase, Y. Butsugan, U. Nagai, Bull. Chem. Soc. Jpn. 1985, 58, 304.
[32] S. G. Davies, S. Wollowitz, Tetrahedron Lett. 1980, 21, 4175.
[33] A. Alexakis, E. Vrancken, P. Mangeney, Synlett 1998, 1165; M. Mizuno, M. Kanai, K. Tomioka, Tetrahedron
1997, 53, 10699.
[34] Z. Zhang, R. Scheffold, Helv. Chim. Acta 1993, 76, 2602.
[35] P. OꢁBrien, C. D. Pilgram, Tetrahedron Lett. 1999, 40, 8427.
[36] F. Camps, E. Chamorro, V. Gasol, A. Guerrero, J. Org. Chem. 1989, 54, 4294.
[37] J. D. Roberts, E. R. Trumbull, W. Bennett, R. Armstrong, J. Am. Chem. Soc. 1950, 72, 3116.
[38] P. Müller, J.-L. Toujas, G. Bernardinelli, Helv. Chim. Acta 2000, 83, 1525.
[39] W. Kirmse, N. Knöpfel, J. Am. Chem. Soc. 1976, 98, 4672.
[40] T. Imamoto, T. Mukaiyama, Chem. Lett. 1980, 45; D. Seebach, G. Jaeschke, A. Pichota, L. Audergon, Helv.
Chim. Acta 1997, 80, 2515; M. Kanai, K. Tomioka, Tetrahedron Lett. 1995, 36, 4273; Q.-L. Zhou, A. Pfaltz,
Tetrahedron 1994, 50, 4467.
[41] a) A. Alexakis, J.-C. Frutos, P. Manganey, Tetrahedron: Asymmetry 1993, 4, 2427; A. Alexakis, J. Vasrtra, J.
Burton, P. Manganey, Tetrahedron: Asymmetry 1997, 8, 3193; A. H. M. de Vries, A. Meetsma, B. L. Feringa,
Angew. Chem., Int. Ed. 1996, 35, 2374; F.-Y. Zhang, A. S. C. Chan, Tetrahedron: Asymmetry 1998, 9, 1179;
b) A. K. H. Knöbel, I. H. Escher, A. Pfaltz, Synlett 1997, 1429; c) B. L. Feringa, M. Pineschi, L. A. Arnold,
R. Imbos, A. H. M. de Vries, Angew. Chem., Int. Ed. 1997, 36, 2620.
[42] F. Badalassi, P. Crotti, F. Macchia, M. Pineschi, A. Arnold, B. L. Feringa, Tetrahedron Lett. 1998, 39, 7795;
F. Bertozzi, P. Crotti, F. Macchia, M. Pineschi, A. Arnold, B. L. Feringa, Org. Lett. 2000, 2, 933.

Helvetica Chimica Acta ± Vol. 84 (2001)
677
[43] S. E. Schaus, E. N. Jacobsen, Org. Lett. 2000, 2, 1001; K. B. Hansen, J. L. Leighton, E. N. Jacobsen, J. Am.
Chem. Soc. 1996, 118, 10924; R. G. Konsler, J. Karl, E. N. Jacobsen, J. Am. Chem. Soc. 1998, 120, 10780.
[44] S. Mori, E. Nakamura, K. Morokuma, J. Am. Chem. Soc. 2000, 122, 7294.
[45] D. F. Shriver, M. A. Drezdon, ꢀThe Manipulation of Air-Sensitive Compoundsꢁ, 2nd edn., J. Wiley & Sons,
New York, 1986.
[46] W. C. Still, M. Khan, A. Mitra, J. Org. Chem. 1978, 43, 2923.
[47] Y. Yamada, T. Yamamoto, M. Okawara, Chem. Lett. 1975, 361.
[48] D. A. Evans, M. M. Faul, M. T. Bilodeau, J. Am. Chem. Soc. 1994, 116, 2742.
[49] B. Zipperer, K.-H. Mueller, B. Gallenkampf, R. Hildebrand, M. Fletschinger, Chem. Ber. 1998, 121, 757.
[50] J. Jeong, B. S. I. Tao, H. Henniges, K. B. Sharpless, J. Am. Chem. Soc. 1998, 120, 6844.
[51] J.-P. Mahy, G. Bedi, P. Battioni, D. Mansuy, J. Chem. Soc., Perkin Trans. 2 1988, 1515.
[52] E. Keller, J. Maurer, R. Naasz, T. Schader, A. Meetsma, B. L. Feringa, Tetrahedron: Asymmetry 1998, 9,
2409.
[53] C. Sacconi, M. Ciampolini, J. Org. Chem. 1963, 28, 276.
[54] H. Fritschi, U. Leutenegger, K. Siegmann, A. Pfaltz, W. Keller, C. Kratky, Helv. Chim. Acta 1988, 71, 1541.
[55] G. N. Weinstein, M. J. OꢁConnor, R. H. Holms, Inorg. Chem. 1970, 9, 2104.
[56] Y. Belokon, N. Ikonnikov, M. Moscalenko, M. Noeth, S. Orlova, Tetrahedron: Asymmetry 1996, 7, 851.
[57] W.-H. Leung, E. Y. Y. Chan, E. K. F. Chow, I. D. Williams, S.-M. Peng, J. Chem. Soc., Dalton Trans. 1966,
1229.
[58] J. F. Larrow, E. N. Jacobsen, Y. Gao, Y. Hong, X. Nie, C. M. Zemp, J. Org. Chem. 1994, 59, 1939; L. Deng,
E. N. Jacobsen, J. Org. Chem. 1992, 57, 4320.
[59] J. Yazhong, G. Liuzhu, F. Xiaoming, H. Wenhao, P. Weidong, L. Zhi, M. Aiqiao, Tetrahedron 1997, 53, 14327.
[60] X.-G. Zhou, J.-S. Huang, P.-H. Ko, K.-K. Cheung, C.-M. Che, J. Chem. Soc., Dalton Trans. 1999, 3303.
[61] D. H. R. Barton, R. S. Hay-Motherwell, W. B. Motherwell, J. Chem. Soc., Perkin Trans. 1 1983, 443.
[62] H. Nohira, E. Ehara, A. Miyashita, Bull. Chem. Soc. Jpn. 1970, 43, 2230.
[63] T. Masamune, M. Ohno, M. Koshi, S. Ohuchi, T. Iwadare, Bull. Chem. Soc. Jpn. 1985, 58, 304.
[64] S. Cerezo, J. Cortes, M. Moreno-ManÄas, R. Pleixats, A. Roslans, Tetrahedron 1998, 49, 14869.
[65] R. A. Abramovitch, G. N. Kraus, M. Pavlin, W. D. Holocomb, J. Chem. Soc., Perkin Trans. 1 1974, 2169.
Received October 12, 2000