The enantioselectivity and the stereochemical course of copper-catalyzed intramolecular CH insertions of phenyliodonium ylides

Article abstract of DOI:10.1002/1522-2675(200202)85:2<483::AID-HLCA483>3.0.CO;2-Q

The Cu-catalyzed intramolecular CH insertion of phenyliodonium ylide 1b was investigated at 0° in the presence of several chiral ligands. Enantioselectivities varied in the range 38-72%, and were higher than those resulting from reaction of the diazo compound 1c at 65°. The intramolecular insertion of the enantiomerically pure methyl diazoacetate (R)-20 and of the corresponding phenyliodonium ylide (R)-21 proceeded to (R)-23 with retention of configuration with [Cu(hfa)₂] (hfa = hexafluoroacetylacetone = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) and [Rh₂(OAc)₄]. These results are consistent with a carbenoid mechanism for the Cu-catalyzed insertion with phenyliodonium ylides. However, the insertion of the perfluorosulfonated phenyliodonium ylide (R)-29 afforded with [Cu(hfa)₂] as well as with [Rh₂(OAc)₄] the cyclopentanone derivative 30 as a cis/trans mixture with only 56-67% enantiomeric excess.

Full text of DOI:10.1002/1522-2675(200202)85:2<483::AID-HLCA483>3.0.CO;2-Q

Helvetica Chimica Acta Vol. 85 (2002)
483
The Enantioselectivity and the Stereochemical Course of
Copper-Catalyzed Intramolecular CH Insertions of Phenyliodonium Ylides
by Paul M¸ller* and Christelle Bole¬a
Department of Organic Chemistry, University of Geneva 30, Quai Ernest-Ansermet, CH-1211, Geneva 4
The Cu-catalyzed intramolecular CHinsertion of phenyliodonium ylide 1b was investigated at 08 in the
presence of several chiral ligands. Enantioselectivities varied in the range 38 72%, and were higher than those
resulting from reaction of the diazo compound 1c at 658. The intramolecular insertion of the enantiomerically
pure methyl diazoacetate (R)-20 and of the corresponding phenyliodonium ylide (R)-21 proceeded to (R)-23
with retention of configuration with [Cu(hfa)2] (hfa ˆ hexafluoroacetylacetone ˆ 1,1,1,5,5,5-hexafluoropen-
tane-2,4-dione) and [Rh2(OAc)4]. These results are consistent with a carbenoid mechanism for the Cu-catalyzed
insertion with phenyliodonium ylides. However, the insertion of the perfluorosulfonated phenyliodonium ylide
(R)-29 afforded with [Cu(hfa)2] as well as with [Rh2(OAc)4] the cyclopentanone derivative 30 as a cis/trans
mixture with only 56 67% enantiomeric excess.
Introduction. The decomposition of diazo compounds in the presence of transition
metals leads to reactions typical for metal-carbenoid intermediates, such as cyclo-
propanations, insertions into XÀHbonds, and formation of ylides with heteroatoms
having lone pairs available. The Cu-catalyzed asymmetric cyclopropanation is probably
the most popular application of the transition-metal-catalyzed carbenoid reactions [1].
In addition, Cu-catalyzed decomposition of diazo compounds may also lead to CH
bond insertions, although RhII catalysts are usually more appropriate for these latter
transformations [2]. The RhII-catalyzed insertion proceeds with retention of config-
uration at the C-atom undergoing the reaction [3], and all the experimental evidence is
consistent with a mechanism involving a rhodium-carbenoid as the reactive inter-
mediate [4]. In contrast, the mechanism of the Cu-catalyzed CHinsertion has not been
investigated systematically, but is assumed to be analogous to that of the reactions
catalyzed by RhII.
Since diazo compounds are potentially explosive, toxic, and cancerogenic [5], the
number of their industrial applications is limited [6]. Phenyliodonium ylides are
potential substitutes for diazo compounds in metal-carbenoid reactions. Their photo-
chemical [7][8], thermal [8][9], and transition-metal-catalyzed [10] decompositions
exhibit analogies to that of diazo compounds, and, accordingly, carbene or carbenoid
intermediates are usually assumed to be involved in these reactions [9 11] although
little effort has been made to demonstrate the involvement of these putative species.
Some years ago, we presented evidence for metal-carbenoid pathways in RhII-catalyzed
cyclopropanation and CHinsertion reactions [11].
The mechanism of the CuI-catalyzed decomposition of phenyliodonium ylides is
controversial. Originally, Hayasi et al. proposed a copper-complexed carbene
intermediate in the CuI-catalyzed decomposition of phenyliodonium ylides derived

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Helvetica Chimica Acta Vol. 85 (2002)
from 1,3-diketones [9]. More recently, Moriarty reported the CuCl-catalyzed intra-
molecular cyclopropanation of olefins with phenyliodonium ylides [12]. Surprisingly,
the reaction took place even in the absence of catalyst, albeit at lower rate. A
mechanism involving electrophilic addition of the iodonium center to the double bond
followed by reductive elimination of PhI was proposed for the uncatalyzed trans-
formation. The catalytic effect of CuI was tentatively ascribed to electron transfer from
the catalyst to the ylide. A carbene or metal-carbenoid mechanism was specifically
ruled out.
Recently, we reported the intramolecular cyclopropanation of unsaturated phenyl-
iodonium ylides derived from acetoacetate and malonate esters with [Cu(OTf)2] (Tf ˆ
CF3SO2) in the presence of chiral ligands [13]. Enantioselectivities of up to 68% were
observed, consistent with a carbenoid mechanism. However, comparison of the
enantioselectivities resulting from ylide decomposition with those of the corresponding
diazo compounds revealed irregularities, suggesting a competing unselective cyclo-
propanation mechanism of unknown nature. Since the cycloaddition mechanism of
Moriarty cannot apply to CHinsertions, and since no spontaneous, uncatalyzed CH
insertions of phenyliodonium ylides have ever been reported, we have now examined
the enantioselectivity and the stereochemistry of intramolecular insertions upon the
CuI-catalyzed decomposition of phenyliodonium ylides in comparison to that of the
corresponding diazo compounds. Some of the results have been reported in preliminary
form [14].
Results and Discussion. Enantioselective CH Insertion of Phenyliodonium Ylide
1b and Diazo Ester 1c. The phenyliodonium ylide 1b was synthesized by reaction of the
hydrocarbon 1a [15] with PhI(OAc)2 [16] as described previously [11a] (Scheme 1).
Exposure of 1b to [Cu(OTf)2] in CH2Cl2 at 08 in the presence of chiral ligands 4 11 and
13 16 or catalyst 12 (Fig.) resulted in intramolecular CHinsertion and afforded the
cyclopentanone carboxylate 2. The keto ester 2 was subjected to hydrolysis and
decarboxylation (HBr/EtOH) to furnish the ketone 3 on which enantiomeric excess
(ee) and the absolute configuration were determined. The diazo compound 1c
corresponding to 1b was obtained via diazo transfer from 1a with TsN3. Owing to the
low reactivity of the CuI catalysts towards diazo compounds, the diazo decomposition
had to be carried out in 1,2-dichloroethane at 658. Unfortunately, the ylide 1b
decomposed at this temperature, and it was impossible to effect the reactions of 1b and
1c under identical conditions. The results are summarized in Table 1.
Scheme 1

Helvetica Chimica Acta Vol. 85 (2002)
485
Figure. Catalyst and Ligands
Table 1. Yields and Enantioselectivities (ee) in Intramolecular CH Insertions of Phenyliodonium Ylide 1b and
Diazo Keto Ester 1c in the Presence of Chiral Ligands L and [Cu(OTf)2]
Run
L
Yield [%] from 1ba)
ee [%]
Yield [%] from 1cb)
ee [%]
Comment
[14]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
4
5
6
7
8
9
10
11
12c)
13
14d)
14e)
15
16
51
56
49
47
52
46
41
55
35
46
47
49
42
11
42 (R)
23 (R)
38 (R)
13 (R)
72 (S)
17 (S)
05 (R)
22 (R)
10 (S)
59 (R)
67 (S)
70 (S)
16 (R)
57 (S)
38
15 (R)
32
18 (R)
14
55
31 (S)
22
[14]
[14]
35
17
60 (R)
51 (S)
32
18 (S)
a) In CH2Cl2, 08. b) In ClCH2CH2Cl, 658. c) Reaction with isolated complex 12. d) de of 14 70%. e) de of
14 >98%.

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In general, we find that the Cu-catalyzed insertions proceed with acceptable yields
from the ylide. The occurrence of CHinsertions upon catalysis with Cu is remarkable in
itself, since CuI complexes are traditionally regarded as the catalysts of choice for
II
cyclopropanations, while CHinsertions are better carried out with Rh catalysts.
However, since 1b and 1c have no competitive cyclopropanation pathway available, the
normally disfavored insertion pathway predominates with CuI catalysts. Other Cu-
catalyzed intramolecular CHinsertions of diazo compounds have been reported [17].
The observation that the yields of insertion product 2 resulting from the reaction of the
ylide 1b are generally higher than those of the diazo decomposition is probably a
consequence of the notorious low reactivity of diazo esters and diazo ketones derived
from b-dicarbonyl compounds, which require temperatures of up to 808 with
[CuI(carboxamidato)] and also with [RhII(carboxamidato)] catalysts [18]. Phenyl-
iodonium ylides react with these catalysts already at 08, and their enhanced reactivity
constitutes the main aspect of their synthetic interest.
In all cases, the absolute configuration of the major enantiomer of the insertion
product 3 obtained from the ylide 1b is identical with that obtained from the diazo
precursor 1c for a given ligand. Inspection of Table 1 shows that the enantioselectivity
resulting from ylide decomposition (at 08) is always higher than that from the
corresponding diazo decomposition (at 658), except for 13, where it is practically equal.
It culminates at 72% ee with ligand 8. The higher selectivity of the ylide 1b corresponds
to expectation on the grounds of the lower temperature of the reactions. In addition,
catalyst stability may become a problem in the diazo decomposition. The low ee×s
observed in some of these reactions may be due to partial degradation of the catalyst at
the temperature required for the reaction to occur. Thus, the intriguing irregularities in
the enantioselectivities of Cu-catalyzed cyclopropanations of phenyliodonium ylides
and diazo compounds do not occur in the CHinsertion reactions.
To the best of our knowledge, these are the first enantioselective CHinsertions ever
observed upon Cu-catalyzed decomposition of phenyliodonium ylides. The results
show clearly that the reactions proceed in the intimate vicinity of the chiral catalyst, and
that the mechanism proposed by Moriarty for intramolecular cyclopropanation of
phenyliodonium ylides does not apply to the CHinsertions. The less than 100% ee
observed for insertion of 1b under optimized conditions may reasonably be ascribed to
an inappropriate choice of catalysts, rather than to a competing reaction of a free
carbene. Although thermolysis of phenyliodonium ylides may result in formation of
free carbenes capable of CHinsertion, this reaction does not occur at 0 8, but requires a
temperature of 1008 [7].
Stereochemistry of the Cu-Catalyzed CH Insertion of Phenyliodonium Ylide (R)-21.
The observation of enantioselective CHinsertions upon decomposition of phenyl-
iodonium ylide 1b in the presence of chiral nonracemic CuI catalysts is consistent with a
mechanism involving a metal-carbenoid as intermediate, but constitutes no proof. The
carbenoid mechanism for insertion requires retention of configuration at the C-atom
undergoing insertion, and this has been observed in the [Rh2(OAc)4]-catalyzed diazo
decomposition of a-diazo-b-keto esters and a-diazo-b-keto sulfones [3]. We have now
investigated the stereochemistry of the CuI-catalyzed intramolecular CHinsertion at
the chiral center of the enantiomerically pure diazo ester (R)-20 and the ylide (R)-21.
The required precursors were synthesized starting with commercially available (À)-

Helvetica Chimica Acta Vol. 85 (2002)
487
(S)-phenylpropan-1-ol ((S)-17), which was converted to the iodide (S)-18 by reaction
with I2 and triphenylphosphine (Scheme 2). Condensation with the dianion prepared
from methyl acetoacetate with lithium diisopropylamide (LDA) in THF and
hexamethylphosphoric triamide (HMPA) as cosolvent gave the substituted keto ester
(R)-19 in 62% yield, and diazo transfer with TsN3/Et3N in MeCN yielded the diazo
precursor (R)-20 (87%). The ylide (R)-21, in turn was isolated as an unstable oil in 75
90% yield upon reaction of (R)-19 with PhI(OAc)2 in MeOH.
Scheme 2
As expected, the diazo precursor (R)-20 reacted smoothly with [Rh2(OAc)4] at 238
to afford the cyclic keto ester (R)-22 in 59% yield (Table 2). The steric course of the
reaction was determined with the ketone (R)-23, which was obtained after hydrolysis
(DMSO/H2O) and decarboxylation of (R)-22. The absolute configuration of (R)-23
was determined by comparison of the optical rotation with that reported in [19]. The
enantiomeric excess as determined by GC was >98%. This corresponds to an overall
retention of configuration for the CHinsertion. The ylide ( R)-21 reacted with
[Rh2(OAc)4] at 08 to afford (R)-22 and, subsequently, (R)-23 with the same
enantioselectivity. The diazo decomposition of (R)-20 with CuI catalysts proceeded
only sluggishly even at elevated temperatures. Optimized conditions (2 mol-% of
[Cu(hfa)2
(Hhfa ˆ hexafluoroacetylacetone ˆ 1,1,1,5,5,5-hexafluoropentane-2,4-di-
one)] in 1,2-dichloroethane at 608, 3 h) resulted in a 54% yield of (R)-22 with
retention of configuration. The ylide (R)-21, in turn, reacted at 08 and furnished (R)-22
with full retention of configuration, albeit with only 36% yield.
Table 2. Decomposition of Diazo Ester (R)-20 and Ylide (R)-21
b
Catalysta)
Solvent, T [8]
Time
Yield of (R)-22 [%]
[a]2D0
)
ee [%]c)
(R)-20
(R)-20
(R)-21
(R)-21
[Rh2(OAc)4]
[Cu(hfa)2]
[Rh2(OAc)4]
[Cu(hfa)2]
CH2Cl2, 23
(CH2Cl)2, 60
CH2Cl2, 0
30 min
3 h
3 h
59
54
57
36
10.2
10.1
10.0
10.1
> 98
> 98
> 98
> 98
CH2Cl2, O
3 h
a) 2 mol-% with respect to substrate; Hfa ˆ 1,1,1,5,5,5-hexafluoropentane-2,4-dione. b) In EtOH, c ˆ 1.00 1.20.
c) by GC.

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The observation of retention of configuration in all these reactions provides strong
evidence for a carbenoid intermediate, while the observation of enantioselectivity in
the insertions pleads in favor of a metal-associated carbene (metal-carbenoid). While
metal-carbenoid intermediates have for a long time been assumed in the CuI-catalyzed
diazo decompositions, retention of configuration has been experimentally observed
only once [20]. That the CuI-catalyzed ylide decomposition proceeds also with
retention of configuration suggests that the same intermediate should be involved in
both reactions. The cyclopropanations with ylides follow in principle the same
carbenoid pathway; however, an uncatalyzed cyclopropanation may intervene via an as
yet unknown mechanism, and result in decreased enantioselectivity in comparison to
that observed in the corresponding diazo decompositions.
Stereochemistry of the Intramolecular CH Insertion of (5R)-Phenyliodonium 1-
[(Nonafluorobutyl)sulfonyl]-2-oxo-5-phenylhexylide. In view of the low stability of the
ylide (R)-21 and the low yield in its CuI-catalyzed intramolecular CHinsertion, we
turned our attention to (perfluoroalkyl)sulfonyl-stabilized phenyliodonium ylides
which, according to the literature, are more stable, but may also be decomposed by
[Cu(acac)2] (Hacac ˆ pentane-2,4-dione) to afford products derived from carbenoid
reactions [21][22]. The required ylide (R)-29 was synthesized as shown in Scheme 3:
Commercially available nonafluorobutanesulfonyl fluoride (24) was reduced with
hydrazine [23] to the sulfinic acid 25, which was alkylated with MeI to afford the
sulfone 26. The sulfone was deprotonated (LDA) and acylated with AcCl to yield the
sulfonyl ketone 27. Double deprotonation of 27 afforded the dianion which was
alkylated in situ with the iodide (S)-18 to give (R)-28 in 53% yield. While diazo transfer
to (R)-28 attempted under a variety of conditions failed, the phenyliodonium ylide (R)-
29 was formed smoothly upon treatment of (R)-28 with Et3N/PhI(OAc)2. The ylide
(R)-29 proved to be remarkably stable and survived purification by flash chromatog-
raphy. Decomposition with [Rh2(OAc)4] at 238 furnished the cyclopentanone 30 in
47% yield as a mixture of stereoisomers having 67 and 68% ee, respectively. The
isomers were separable by chromatography, but interconverted slowly upon standing in
solution. The relative configuration was assigned by NMR: The cis-isomer showed a
NOE between the quaternary Me group and the proton at C(2). Decomposition of
(R)-29 with [Cu(hfa)2], in turn, afforded 30 in 56% yield (trans/cis ratio 81:19) with
Scheme 3

Helvetica Chimica Acta Vol. 85 (2002)
489
enantioselectivities of 67 (trans-isomer) and 56% (cis-isomer), respectively. Surpris-
ingly, the desulfonation of 30 under a large variety of conditions failed, and the
absolute configuration could not be determined.
The possibility that the partial racemization of 30 could be due to a ring-opening
and ring-closing process after carbenoid insertion was ruled out by redetermination of
its enantiomer composition, which remained unchanged even after several weeks. The
partial loss of stereochemical integrity on the way from (R)-29 to 30 must, therefore, be
attributed to the insertion process itself. Since partial racemization occurs also with RhII
catalysts, the phenomenon should not be ascribed to an effect due to the involvement of
the Cu-atom. Furthermore, the presence of the sulfonyl substituent alone should not be
responsible for partial racemization, since RhII-catalyzed insertion of a diazo keto
sulfone reportedly proceeds with full retention of configuration [24]. On the other
hand, unexpected reactions of (perfluorobutyl)sulfonyl-substituted phenyliodonium
ylides involving carbenium ions have been reported: thus, decomposition of the
phenyliodonium ylide derived from ethyl [(nonafluorobutyl)sulvonyl]acetate in the
presence of [Cu(OTf)2] and olefins affords lactones, arising from intermediate
carbenium ions, rather than the expected cyclopropanes [22]. A few examples of
RhII-catalyzed diazo decompositions proceeding via hydride transfer to stabilized
carbenium ions have been observed [25], and an alternative mechanism for CH
insertion, involving an intermediate zwitterion, subsequent to hydride transfer has been
proposed [26]. Conceivably, the presence of the strongly electron-attracting (per-
fluorobutyl)sulfonyl group could enforce such a mechanism in the case of (R)-29.
However, a radical mechanism cannot be ruled out on the grounds of the present
results. At this time, and until contrary evidence becomes available, we believe that the
retention mechanism as observed for the RhII- and CuI-catalyzed decomposition of
(R)-20 and (R)-21 is representative, and the partial racemization occurring in the case
of (R)-29 should be considered exceptional.
This work was supported by the Swiss National Science Foundation (Grant Nos. 20-52581.97 and 2027-
048156) and by the European Commission for Science, Research, and Development (COST Action D12). The
authors are indebted to A. Pinto and J.-P. Saulnier for the NMR spectra, D. Klink for the mass spectra, and to
P. G. Andersson for a sample of ligand 10.
Experimental Part
1. General. See [27]. TsN3 was prepared according to the procedure of McElwee-White and Dougherty [28].
The 2-methyl-1-(1-methylethyl)propyl 3-oxobutanoate was synthesized as described previously [29]. Non-
afluoro-4-(methylsulfonyl)butane (26) was prepared via hydrazine reduction of nonafluorobutanesulfonyl
fluoride (Aldrich) and alkylation of the resulting sulfinic acid with methyl iodide, as described by Harzdorf et al.
[23].
2. Ligands and Catalysts. The ligands and catalysts were either purchased (sparteine (16)) or prepared
according to literature procedures: 4, 5, and 7, [30]; 6, [14]; 8, [31]; 9, [32]; 11, [33]; 12, [34]; 13 and 14, [13b]; 15,
[35]; ligand 10 was kindly provided by P. G. Andersson [36].
3. Intramolecular CH Insertion of Phenyliodonium Ylide 1b and Diazo Acetoacetate 1c. 2-Methyl-1-(1-
methylethyl)propyl 3-Oxo-6-phenylhexanoate (1a) [11a]. To diisopropylamine (8.47 ml, 59.9 mmol) in THF
(40 ml) at À788, 1.6m BuLi in hexane (34.3 ml, 54.9 mmol) was added, and the mixture was stirred for 15 min.
Then 2-methyl-1-(1-methylethyl)propyl 3-oxobutanoate (5.00 g, 25.0 mmol) in THF (10 ml) was added at À788.
After stirring for 30 min, (2-bromoethyl)benzene (13.9 g, 74.9 mmol) in THF (10 ml) was added at once, and
stirring was maintained at À788 for 10 min. The mixture was decomposed with 2n HCl (30 ml) with cooling at
08. The aq. phase was extracted with CH2Cl2 (3 Â 50 ml), the combined org. phase dried (MgSO4), and

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evaporated, and the residue distilled to remove the remaining (2-bromoethyl)benzene and then purified by FC
(pentane/AcOEt 97 :3): 1a (7.22 g, 95%). Colorless oil. 1H-NMR (500 MHz, CDCl3): 0.86 (d, J ˆ 6.9, 6 H); 0.90
(d, J ˆ 6.9, 6 H); 1.84 1.99 (m, 4 H); 2.58 (t, J ˆ 7.3, 2 H); 2.65 (t, J ˆ 7.3, 2 H); 3.45 (s, 2 H); 4.63 (dd, J ˆ 6.0,
6.3, 1 H); 7.16 7.32 (m, 3 H); 7.26 7.32 (m, 2 H ).13C-NMR (125 MHz, CDCl3): 17.2 (q); 19.5 (q); 24.8 (t); 29.3
(d); 34.8 (t); 42.3 (t); 49.3 (t); 84.1 (d); 126.0 (d); 128.3 (d); 128.4 (d); 141.3 (s); 172.9 (s); 178.3 (s); 202.6 (s).
MS: 189 (18), 188 (34), 148 (9), 147 (78), 128 (12), 105 (13), 104 (100), 102 (19), 99 (14), 98 (16), 91 (40), 84
(16), 83 (10), 73 (12), 57 (94), 55 (12).
Phenyliodonium 1-[2-Methyl-1-(1-methylethyl)propoxy]-1,3-dioxo-6-phenylhexylide (1b) [11a]. To KOH
(257 mg, 3.94 mmol) in MeOH(5.0 ml) at 0 8, 1a (300 mg, 0.98 mmol) in MeOH(10 ml) was added
slowly. PhI(OAc)2 (317 mg, 0.98 mmol) was added in portions. After stirring for 5 min, the mixture was poured
on ice/H2O (10 ml). Extraction with CH2Cl2 (2 Â 10 ml), drying (MgSO4), and evaporation afforded 1b (496 mg,
80%). Thick yellow oil. 1H-NMR (200 MHz, CDCl3): 0.80 (d, J ˆ 6.9, 6 H); 0.85 (d, J ˆ 6.9, 6 H); 1.80 2.04
(m, 4 H); 2.68 (t, J ˆ 7.3, 2 H); 2.92 (t, J ˆ 7.3, 2 H); 4.73 (dd, J ˆ 6.0, 6.4, 1 H); 7.17 7.52 (m, 5 H); 7.39 7.77
(m, 5 H ).
2-Methyl-1-(1-methylethyl) 2-Diazo-3-oxo-6-phenylhexanoate (1c) [11a]. The soln. of 1a (3.00 g,
9.85 mmol) in MeCN (10 ml) was added to TsN3 (1.94 g, 9.85 mmol) and Et3N (2.75 ml, 19.7 mmol) at r.t.
The mixture was stirred overnight. It was poured into aq. NaOHsoln. (10 ml), the aq. layer extracted with Et 2O
(3 Â 20 ml), and the combined org. phase dried (Na2SO4) and evaporated. FC (pentane/AcOEt 99 :1) of the
residue yielded 1c (3.26 g, 89%). Yellow oil. IR (NaCl): 3025w, 2967m, 2135s, 1709s, 1645m, 1372m, 1121m,
985w. 1H-NMR (500 MHz, CDCl3): 0.89 (d, J ˆ 6.7, 6 H); 0.93 (d, J ˆ 6.9, 6 H); 1.92 2.04 (m, 4 H); 2.68 (t, J ˆ
7.3, 2 H); 2.90 (t, J ˆ 7.3, 2 H); 4.71 (dd, J ˆ 6.0, 6.3, 1 H); 7.17 7.22 (m, 3 H); 7.26 7.31 (m, 2 H ). 13C-NMR
(125 MHz, CDCl3): 17.2 (q); 19.5 (q); 25.9 (t); 29.4 (d); 35.2 (t); 39.7 (t); 84.3 (d); 125.9 (d); 128.3 (d); 128.4 (d);
141.7 (s); 161.6 (s); 192.8 (s). MS: 226 (15), 204 (38), 187 (49), 186 (47), 159 (13), 158 (17), 147 (35), 128 (29),
117 (12), 104 (19), 99 (18), 98 (15), 91 (74), 83 (42), 65 (11), 58 (10), 57 (100), 55 (16).
3-Phenylcyclopentanone (3) via Decomposition of 1b. A soln. of (p)-2,2'-([1,1'-binaphthalene]-2,2'-
diyl)bis[(4S)-4-(cyclohexylmethyl)-4,5-dihydrooxazole] (13; 7.4 mg, 11 mmol) and [Cu(OTf)2] (3.9 mg,
11 mmol) in CH2Cl2 (6.0 ml), was stirred for 1 h at r.t. The ylide 1b (0.54 mmol) in CH2Cl2 (6.0 ml) was added
at 08, and the mixture was stirred overnight at 08. The solvent was evaporated and the residue purified by FC
(pentane/AcOEt 97:3) to give crude keto ester 2 (77 mg, 47%) as colorless oil. The crude 2 (77 mg) was
refluxed in a mixture of HBr (2.5 ml) and EtOH (8.0 ml). After cooling, the mixture was extracted with CH2Cl2
(3 Â 10 ml), the org. phase washed with H2O (2 Â 10 ml), dried (MgSO4), and evaporated, and the residue
purified by FC (pentane/AcOEt 90 :10): 3 [11a] (26 mg, 64%) of 67% ee. Colorless oil. GC (Lipodex B
(Macherey-Nagel), 1308): tR 12.1 ((S)-3) and 13.7 ((R)-3). [a]2D0 ˆ ‡69.1 (c ˆ 1.04, CHCl3) for 67% ee ([15a]:
[a]2D2 ˆ ‡69.4 (c ˆ 1.42, CHCl3) for (R)-3 with 76% ee). 1H-NMR (200 MHz, CDCl3): 1.87 2.11 (m, 1 H );
2.18 2.55 (m, 4 H); 2.66 (dd, J ˆ 18.8, 15.5, 1 H); 3.30 3.52 (m, 1 H); 7.18 7.42 (m, 5 H ).13C-NMR (100 MHz,
CDCl3): 31.0 (t); 38.6 (t); 42.0 (d); 45.6 (t); 126.6 (d); 128.5 (d); 143.0 (s); 217.7 (s).
3-Phenylcyclopentanone (3) via Diazo Decomposition of 1c. Ligand 13 (4.2 mg, 7.2 mmol) and [Cu(OTf)2]
(2.2 mg, 6.0 mmol) in ClCH2CH2Cl (3.0 ml) was stirred at r.t. for 1 h, then heated to 658. The diazo ester 1c
(100 mg, 0.30 mmol) in ClCH2CH2Cl (3.0 ml) was added at once, and the mixture was stirred at 658 for 1 d.
After evaporation, the crude keto ester 2 (32 mg, 35%) was obtained, which was converted to 3 as described
above in 70% yield and with 60% ee. [a]2D0 ˆ ‡65.4 (c ˆ 1.06) for 60% ee.
4. Intramolecular CH Insertion with (R)-20 and (R)-21. (S)-(2-Iodo-1-methylethyl)benzene ((S)-18). To
Ph3P (30.8 g, 117 mmol) and 1H-imidazole (8.00 g, 117 mmol) in Et2O (100 ml) and MeCN (40 ml), I2 (22.4 g,
88.1 mmol) was added in portions at r.t. The resulting suspension was stirred for 1 h, and (À)-(S)-2-
phenylpropanol ((S)-17; 4.00 g, 29.4 mmol) in Et2O (40 ml) was added dropwise. The mixture was stirred for
3 h, after which it was diluted with petroleum ether (500 ml). The soln. was filtered, the filtrate evaporated, and
the residue purified by distillation (103 1058/4 Torr): (S)-18 (6.12 g, 85%). Colorless oil. [a]2D0 ˆ À31.8 (c ˆ 1.67,
CHCl3). IR (NaCl): 3026m, 2964s, 2866m, 1494m, 1451m, 1376m, 1179s, 759s, 698s. 1H-NMR (400 MHz,
CDCl3): 1.44 (d, J ˆ 6.9, 3 H); 3.01 3.11 (m, 1 H); 3.34 (dd, J ˆ 7.9, 9.3, 1 H); 3.42 (dd, J ˆ 6.4, 9.4, 1 H); 7.19
7.38 (m, 5 H ).13C-NMR (100 MHz, CDCl3): 14.7 (t); 21.6 (q); 42.4 (d); 126.7 (d); 126.9 (d); 128.6 (d); 144.4 (s).
.
‡
MS: 246 (3, M ), 120 (9), 119 (88), 105 (26), 104 (13), 103 (9), 92 (8), 91 (100), 79 (8), 78 (7), 77 (11), 51 (10).
‡
HR-MS: 245.9894 (C9H11I ; calc. 245.9905).
(R)-Methyl 3-Oxo-6-phenylheptanoate ((R)-19). A soln. of 1.6m BuLi in hexane (29.0 ml, 46.5 mmol,
4 equiv.) was added to diisopropylamine (6.90 ml, 48.8 mmol, 4.2 equiv.) in THF (50 ml) at 08. After 20 min, the
mixture was cooled to À258, and methyl 3-oxobutanoate (2.50 ml, 23.2 mmol, 2 equiv.) was added. The temp.
was raised to 08, the mixture was stirred for 30 min, and HMPA (8.13 ml, 46.5 mmol, 4 equiv.) was added. After

Helvetica Chimica Acta Vol. 85 (2002)
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5min, the soln. was added to (S)-18 (2.86 mg, 11.6 mmol) in THF (10 ml) at 08. After stirring at r.t. for 1 h, the
mixture was neutralized with sat. NH4Cl soln. The aq. layer was extracted with AcOEt (3 Â 100 ml) and the
combined org. layer dried (MgSO4) and evaporated to give (R)-19 (2.05 g, 54%) after FC (petroleum ether/
AcOEt 95 :5). [a]2D0 ˆ À18.3 (c ˆ 1.00, CHCl3). IR (NaCl): 3026m, 2956s, 2872m, 1748s, 1716s, 1452m, 1436m,
1
1319m, 1192m, 764m, 702s. H-NMR (400 MHz, CDCl3): 1.28 (d, J ˆ 6.8, 3 H); 1.81 2.01 (m, 2 H); 2.33 2.51
(m, 2 H); 2.66 2.77 (m, 1 H); 3.37 (s, 2 H); 3.72 (s, 3 H); 7.16 7.25 (m, 3 H); 7.27 7.35 (m, 2 H ). 13C-NMR
(100 MHz, CDCl3): 22.2 (q); 31.4 (t); 39.1 (d); 41.1 (t); 48.9 (t); 52.2 (q); 126.1 (d); 126.9 (d); 128.4 (d); 146.1 (s);
.
‡
167.5 (s); 202.5 (s). MS: 234 (1, M ), 216 (11), 161 (16), 142 (15), 119 (25), 118 (100), 117 (19), 116 (29), 106
(7), 105 (71), 104 (6), 103 (11), 101 (8), 91 (22), 84 (11), 79 (12), 78 (9), 77 (15), 69 (7), 59 (16), 55 (8), 51 (6).
‡
HR-MS: 234.1274 (C14H18O3 ; calc. 234.1256).
(R)-Methyl 2-Diazo-3-oxo-6-phenylheptanoate ((R)-20). The soln. of (R)-19 (300 mg, 1.28 mmol) in
MeCN (10 ml) was added to TsN3 (954 mg, 4.83 mmol) and Et3N (37 ml, 0.26 mmol) in MeCN, and the mixture
was stirred overnight. It was then poured into 10% NaOHsoln. (10 ml). The aq. phase was extracted with Et 2O
(3 Â 20 ml), the combined org. layer dried (Na2SO4) and evaporated, and the residue purified by FC (petroleum
ether/AcOEt 97:3): (R)-20 (292 mg, 88%). Yellow oil. [a]2D0 ˆ À21.6 (c ˆ 1.52, CHCl3). IR (NaCl): 3027m,
1
2958s, 2930m, 2135s, 1723s, 1657s, 1494m, 1436s, 1378s, 1310s, 1216m, 701s. H-NMR (400 MHz, CDCl3): 1.28
(d, J ˆ 6.9, 3 H); 1.89 1.97 (m, 2 H); 2.65 2.86 (m, 3 H); 3.80 (s, 3 H); 7.17 7.23 (m, 3 H); 7.26 7.33 (m, 2 H ).
13C-NMR (100 MHz, CDCl3): 22.1 (q); 32.6 (t); 38.4 (t); 39.4 (d); 52.1 (q); 126.1 (d); 127.0 (d); 128.4 (d); 146.5
‡
(s); 161.7 (s); 192.6 (s). MS: 232 (4, [M À N2] ), 217 (23), 185 (69), 155 (10), 142 (38), 129 (13), 123 (12), 118
(31), 117 (21), 115 (10), 113 (10), 106 (11), 105 (100), 104 (11), 103 (18), 101 (17), 99 (15), 91 (50), 79 (18), 77
‡
(28), 69 (10), 59 (21), 55 (22). HR-MS: 232.1105 (C14H16O3 ; calc. 232.1099).
(R)-Phenyliodonium 1-Methoxy-1,3-dioxo-6-phenylheptylide ((R)-21). To KOH(112 mg, 1.71 mmol) in
MeOH(1.5 ml) at À208, (R)-19 (100 mg, 0.43 mmol) in MeOH(1.0 ml) and PhI(OAc) 2 (137 mg, 0.43 mmol) in
MeOH(1.5 ml) were slowly added. The mixture was stirred for 10 min at 0 8 and then poured into H2O, and the
aq. phase was extracted with CH2Cl2 (3 Â 10 ml). The combined org. phase was dried (MgSO4) and evaporated:
1
187 mg (76%) of (R)-21. Yellow oil. H-NMR (200 MHz, CDCl3): 1.27 (d, J ˆ 6.9, 1 Me); 1.87 2.01 (m, 2 H );
2.65 3.10 (3 H); 3.60 (s, 1 Me); 7.07 7.42 (8 H, CH); 7.43 7.80 (2 H, CH).
Intramolecular Insertion of Diazo Ester (R)-20: (R)-3-Methyl-3-phenylcyclopentanone ((R)-23). To
[Cu(hfa)2] (5.0 mg, 0.01 mmol) in ClCH2CH2Cl (2.0 ml) at 608, (R)-20 (130 mg, 0.50 mmol) in ClCH2CH2Cl
(2.0 ml) was added. The mixture was stirred at 608 for 3 h. After evaporation of the solvent, the residue was
purified by FC (petroleum ether/AcOEt 90 :10) to give (R)-22 (63 mg, 54%), which was heated to reflux in
DMSO (500 ml) and H2O (4.0 ml) for 1 d. After cooling, the mixture was extracted with CH2Cl2 (3 Â 7 ml) and
the combined org. layer washed with H2O (2 Â 5 ml), dried (MgSO4), and evaporated: (R)-23 (32 mg, 68%)
with >98% ee. Colorless oil. GC (Supelco Gamma-DEX, 1008): tR 147.6 ((R)-23), 150.8 ((S)-23). [a]2D0 ˆ ‡10.1
(c ˆ 1.05, EtOH) ([19]: [a]2D0 ˆ ‡10 (c ˆ 1.1, EtOH)). IR (NaCl): 2958m, 1742s, 1496m, 1445m, 1406m, 1159m,
767s, 701s. 1H-NMR (500 MHz, CDCl3): 1.40 (s, 3 H); 2.24 2.35 (m, 2 H); 2.35 2.49 (m, 2 H); 2.49 (d, J ˆ 17.6,
1 H); 2.67 (d, J ˆ 17.3, 1 H); 7.22 7.28 (m, 1 H); 7.29 7.33 (m, 2 H); 7.33 7.38 (m, 2 H ).13C-NMR (125 MHz):
29.4 (q); 35.8 (t); 36.7 (t); 43.8 (s); 52.2 (t); 125.5 (d); 126.3 (d); 128.6 (d); 148.5 (s); 218.5 (s). MS: 174 (81), 159
(23), 145 (15), 132 (8), 131 (24), 119 (14), 118 (100), 117 (42), 116 (9), 115 (15), 104 (7), 103 (17), 91 (26), 78
‡
(12), 77 (15), 65 (7), 58 (11), 57 (9), 56 (25), 51 (14). HR-MS: 174.1044 (C12H14O ; calc. 174.1045).
Decomposition of (R)-20 with [Rh2(OAc)4] in CH2Cl2 at r.t., followed by hydrolysis as above afforded (R)-
23 in 65% yield and with >98% ee. [a]2D0 ˆ ‡10.2 (c ˆ 1.00, EtOH).
Intramolecular Insertion of Phenyliodonium Ylide (R)-21. A soln. of [Cu(hfa)2] (3.0 mg, 60 mmol) in
CH2Cl2 (2.0 ml) was added, at 08, to (R)-21 (131 mg, 0.30 mmol) in CH2Cl2 (2.0 ml). After 3 h, the solvent was
evaporated and the keto ester (R)-22 decarboxylated as described above to afford (R)-23 (13 mg, 64%) with
>98% ee. [a]2D0 ˆ ‡10.1 (c ˆ 1.20, EtOH).
Under the same conditions, ylide (R)-21 (131 mg, 0.30 mmol) reacted in the presence of [Rh2(OAc)4]
(2.9 mg, 6.0 mmol) to afford (R)-23 (21 mg, 69%) with >98% ee. [a]2D0 ˆ ‡10.0 (c ˆ 1.10, EtOH).
5. Intramolecular Insertion with [(Nonafluorobutyl)sulfonyl]-Substituted Ylide (R)-29. 1-[(Nonafluoro-
butyl)sulfonyl]propan-2-one (27). BuLi (56.2 ml, 1.6m, 90 mmol) in hexane was added, at À788, to diisopropyl-
amine (13.9 ml, 98.1 mmol) in THF (60 ml). The mixture was warmed to 08 for 30 min and cooled again to À788.
Sulfone 26 (12.2 g, 40.9 mmol) in THF (60 ml) was added slowly, and stirring was continued for 30 min. Freshly
distilled acetyl chloride (2.90 ml, 36.7 mmol) was added dropwise at À788. After 1 h of stirring, the mixture was
warmed to r.t. within 1 h. The solvent was evaporated, the residue dissolved in Et2O (100 ml), and 1m HCl
added. The aq. layer was extracted with Et2O (3 Â 150 ml), the combined org. layer washed (H2O), dried
(MgSO4), and evaporated, and the residue distilled (1228/20 Torr): 27 (10.5 g, 76%). Colorless solid. IR

492
Helvetica Chimica Acta Vol. 85 (2002)
(CHCl3): 3013w, 1737m, 1378s, 1241s, 1202m, 1143s, 1115m, 784m, 742m. 1H-NMR (500 MHz, CDCl3): 2.50
(s, 3 H); 4.30 (s, 2 H ).13C-NMR (125 MHz): 31.5 (q); 61.8 (t); 191.3 (s). 19F-NMR (532 MHz, CDCl3): 37.8 37.9
‡
(m, 2 F); 42.6 42.7 (m, 2 F); 52.1 52.2 (m, 2 F); 83.0 83.1 (m, 3 F). ESI-MS (pos.): 338.9 ([M À H] ,
‡
C7H4F9O3S ; calc. 338.9).
(R)-1-[(Nonafluorobutyl)sulfonyl]-5-phenylhexan-2-one ((R)-28). A soln. of 1.6m BuLi in hexane
(23.9 ml, 38.2 mmol) was added to diisopropylamine (5.67 ml, 40.1 mmol) in THF (40 ml) at 08. After stirring
for 20 min, the mixture was cooled to À258, and 27 (6.50 g, 19.1 mmol) in THF (20 ml) was added slowly. After
30 min of stirring, HMPA (6.69 ml, 38.2 mmol) was added at 08. Subsequently the dianion resulting from double
deprotonation of 27 was added to the iodide (S)-18 (2.35 g, 9.55 mmol) at 08, and the mixture was stirred at r.t.
for 1 h. After evaporation of the solvent, the residue was dissolved in Et2O (200 ml), and 1m HCl was added until
pH1 was reached. The aq. phase was extracted with Et 2O, the combined org. phase washed (H2O), dried
(MgSO4), and evaporated, unreacted 27 removed by distillation (1228/20 Torr), and the residue purified by FC
(pentane/AcOEt 90 :10) followed by recrystallization: (R)-28 (2.90 g, 53%). Colorless solid. [a]2D0 ˆ À7.2 (c ˆ
1
1.11, CHCl3). IR (CHCl3): 3014s, 1730w, 1602w, 1378m, 1241s, 1210s, 1143m, 778s, 754s. H-NMR (500 MHz,
CDCl3): 1.30 (d, J ˆ 7.0, 3 H); 1.86 1.96 (m, 1 H); 1.96 2.05 (m,1 H); 2.59 (ddd, J ˆ 8.5, 18.6, 27.1, 1 H); 2.61
(ddd, J ˆ 8.5, 18.6, 27.1, 1 H); 2.69 2.78 (m, 1 H); 4.13 (s, 2 H); 7.17 (d, J ˆ 6.9, 2 H); 7.23 (dd, J ˆ 7.2, 7.5, 1 H);
7.32 (dd, J ˆ 7.2, 7.8, 2 H). 13C-NMR (125 MHz): 22.3 (q); 31.3 (t); 39.0 (d); 42.9 (t); 60.8 (t); 126.5 (d); 127.0 (d);
128.7 (d); 146.5 (s); 193.8 (s). 19F-NMR (532 MHz, CDCl3): 37.8 37.9 (m, 2 F); 42.5 42.7 (m, 2 F); 52.0 52.1
‡
‡
(m, 2 F); 83.1 (t, J ˆ 9.7, 3 F). ESI-MS (pos.): 492.8 ([M ‡ Cl] , C16H15F9O3S ; calc. 493.0). Anal. calc. for
C16H15F9O3S: C 41.93, H3.30; found: C 41.86, H3.43.
(R)-Phenyliodonium 1-[(Nonafluorobutyl)sulfonyl]-2-oxo-5-phenylhexylide ((R)-29). To (R)-28 (356 mg,
0.78 mmol) in CH2Cl2 (7.0 ml) at r.t., Et3N (61.0 ml, 0.44 mmol) and PhI(OAc)2 (248 mg, 0.78 mmol) were added
slowly. After 10 min of stirring, the mixture was evaporated and the crude product purified by FC (pentane/
AcOEt 70 :30): (R)-29 (385 mg, 75%). Yellow oil. [a]2D0 ˆ À11.1 (c ˆ 1.13, CHCl3). IR (CHCl3): 3014s, 1730w,
1602w, 1378m, 1241s, 1210s, 1143m, 778s, 754s. 1H-NMR (500 MHz, CDCl3): 1.25 (d, J ˆ 7.0, 3 H); 1.80 2.04
(m, 2 H); 2.52 3.03 (m, 3 H); 7.16 (d, J ˆ 7.9, 1 H); 7.17 (d, J ˆ 7.9, 2 H); 7.23 7.29 (m, 2 H); 7.41 7.47
(m, 2 H); 7.59 7.64 (m, 1 H, CH); 7.95 (d, J ˆ 7.6 ) . 13C-NMR (125 MHz, CDCl3): 21.9 (q); 34.3 (t); 34.5 (t); 39.5
(d); 114.0 (s); 125.9 (d); 127.0 (d); 128.3 (d); 131.9 (d); 132.6 (d); 134.6 (d); 146.8 (s); 189.5 (s). 19F-NMR
(532 MHz, CDCl3): 37.8 37.9 (m, 2 F); 43.0 43.1 (m, 2 F); 50.5 52.8 (m, 2 F); 83.0 (t, J ˆ 9.7, 3 F). Anal. calc.
for C22H18F9IO3S: C 40.02, H2.96; found: C40.29, H2.96.
Intramolecular Insertion with Ylide (R)-29: (R)-3-Methyl-2-[(nonafluorobutyl)sulfonyl]-3-phenylcyclo-
pentanone (30). To [Cu(hfa)2] (2.9 mg, 5.8 mmol) in CH2Cl2 (7.0 ml) at r.t., ylide (R)-29 (192 mg, 0.29 mmol) in
CH2Cl2 (7.0 ml) was added. After stirring for 2 h, the mixture was evaporated and the residue purified by FC
(petroleum ether/AcOEt 95 :5): 30 (74 mg, 56%) in a trans/cis ratio of 81:19. GC (trans-30 (67% ee); Supelco
Beta-DEX, 1308): tR 149.3 and 151.9. GC (cis-30 (56% ee); Supelco Beta-DEX, 1508): tR 119.2 and 121.4. IR
(NaCl): 3018s, 1732w, 1605w, 1384m, 1240s, 1215s, 1141m, 781s, 756s. Anal. calc. for C16H13F9O3S: C 42.11,
H2.87; found: C 41.90, H3.51.
Data of trans-30: Colorless oil. 1H-NMR (500 MHz, CDCl3): 1.76 (s, 3 H); 2.30 2.37 (m, 1 H); 2.44 2.52
(m, 1 H); 3.08 3.17 (m, 1 H); 3.36 3.46 (m, 1 H); 5.72 (s, 1 H); 7.27 7.31 (2 H); 7.32 7.37 ( m, 1 H); 7.38 7.42
(m, 2 H ). 13C-NMR (125 MHz): 28.4 (q); 31.0 (d); 36.6 (d); 90.1 (t); 94.4 (t); 124.0 (d); 128.0 (d); 128.8 (d);
142.8 (s); 182.9 (s). 19F-NMR (532 MHz, CDCl3): 37.7 37.8 (m, 2 F); 42.4 42.7 (m, 2 F); 49.3 49.4 (m, 2 F);
83.0 (t, J ˆ 9.7, 3 F).
Data of cis-30: Colorless oil. 1H-NMR (500 MHz, CDCl3): 1.77 (s, 3 H); 2.29 2.38 (m, 1 H); 2.44 2.51
(m, 1 H); 2.81 2.90 (m, 1 H); 2.95 3.04 (m, 1 H); 5.25 (s, 1 H); 7.29 7.34 (m, 1 H); 7.35 7.40 (m, 4 H ).
13C-NMR (125 MHz): 28.7 (q); 33.5 (d); 35.9 (d); 87.6 (t); 96.9 (t); 124.0 (d); 127.9 (d); 128.7 (d); 142.9 (s); 178.3
(s). 19F-NMR (532 MHz, CDCl3): 37.6 37.9 (m, 2 F); 42.3 42.5 (m, 2 F); 49.2 49.6 (m, 2 F); 83.0 (t, J ˆ 9.7,
3 F). MS: 441 (2), 239 (6), 238 (14), 237 (100), 173 (24), 172 (9), 171 (28), 170 (7), 157 (15), 155 (6), 142 (6),
131 (31), 130 (9), 129 (23), 128 (7), 117 (16), 116 (7), 115 (15), 105 (25), 103 (8), 91 (31), 89 (6), 77 (15), 69
‡
(14), 55 (16), 53 (6), 51 (8). HR-MS: 441.0157 ([C16H13F9SO3 À Me] ; calc. 441.0207).
The same procedure, starting with (R)-29 (192 mg, 0.29 mmol) and [Rh2(OAc)4] (2.8 mg, 5.8 mmol)
afforded 30 in 47% yield, ee (trans) ˆ 67%, ee (cis) ˆ 68%.

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Received August 17, 2001