Synthesis of α-nitro-α-diazocarbonyl derivatives and their applications in the cyclopropanation of alkenes and in O - H insertion reactions

Article abstract of DOI:10.1002/hlca.200290023

A facile and highly efficient method for the preparation of α-nitroα-diazocarbonyl derivatives by a diazotransfer reaction involving (trifluoromethyl) sulfonyl azide has been developed. These substrates undergo a rhodium-catalyzed cyclopropanation reaction with a variety of alkenes. A systematic study of the reaction indicated that the diastereoselectivity of the cyclopropanation could be effectively controlled through the modification of the steric bulk of the diazo reagent. A novel O - H insertion reaction of the metal - carbene complex derived from the α-nitro-α-diazocarbonyl reagent afforded the corresponding novel α-nitro-α-alkoxy carbonyl derivatives.

Full text of DOI:10.1002/hlca.200290023

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Helvetica Chimica Acta Vol. 85 (2002)
Synthesis of a-Nitro-a-diazocarbonyl Derivatives and Their Applications in
the Cyclopropanation of Alkenes and in OÀH Insertion Reactions
by Andre¬ B. Charette*, Ryan P. Wurz, and Thierry Ollevier
¬
¬
¬
¬
¬
Departement de Chimie, Universite de Montreal, P.O. Box 6128, Station Downtown, Montreal (Quebec),
Canada H3C 3J7
(tel: (514)343-2432; fax: (514)343-5900; e-mail: andre.charette@umontreal.ca; http://charette.corg.umontreal.ca)
Dedicated to Professor Dieter Seebach on the occasion of his 65th birthday
A facile and highly efficient method for the preparation of a-nitro-a-diazocarbonyl derivatives by a diazo-
transfer reaction involving (trifluoromethyl)sulfonyl azide has been developed. These substrates undergo a
rhodium-catalyzed cyclopropanation reaction with a variety of alkenes. A systematic study of the reaction
indicated that the diastereoselectivity of the cyclopropanation could be effectively controlled through the
modification of the steric bulk of the diazo reagent. A novel OÀH insertion reaction of the metalÀcarbene
complex derived from the a-nitro-a-diazocarbonyl reagent afforded the corresponding novel a-nitro-a-alkoxy
carbonyl derivatives.
Introduction. In recent years, diazo carbonyl chemistry [1] has been extensively
exploited in several transformations such as in CÀH insertions, cyclopropanations1),
cascade reactions [3], XÀX (BrÀBr, IÀI) [4] and YÀH insertions (Yˆ O, N, S , P, S e,
Si)2), epoxidations [6], aziridinations [7], and in rearrangements or transfer reactions
involving ylides3). The largest body of literature encompasses the chemistry of a-diazo
carbonyl, a-alkyl/aryl-a-diazocarbonyl, or a-vinyl-a-diazocarbonyl reagents, and it
demonstrates exceptional versatility. Our research group has recently become
interested in the preparation and synthetic applications of a-nitro-a-diazo carbonyls
for the expedient synthesis of 2-substituted 1-aminocyclopropanecarboxylic acids (1)
by reduction of the corresponding a-nitrocyclopropanecarboxylic acid 2 (Scheme 1)4).
Additionally, the nitro compound could serve as a possible useful synthon towards the
preparation of isoxazoline N-oxides 3 [10]5), leading to g-hydroxyamino acids 4 [11] or
other g-substituted amino acids 5 (Scheme 1) [12].
The simplest member of the class of constrained a-amino acids is the naturally
occurring 1-aminocyclopropanecarboxylic acid (ACC, 6)6). ACC, a natural plant
growth hormone [14], was found to be a precursor for the biosynthesis of ethylene.
1
)
)
)
)
)
)
For a review, see [2].
2
3
4
5
6
For a review, see [5a]; for examples of NÀH insertions, see [5b,c].
For reviews, see [8].
For R ˆ H, see [9].
See also [23].
First isolation, see [13].

Helvetica Chimica Acta Vol. 85 (2002)
4469
Scheme 1
Applications of ACCs include their introduction into peptides to effect a change in
the NÀCÀCÀO dihedral angle relative to that of natural amino acid units in the
peptide. The rigidity of the cyclopropane ring favors small f and y angles (7), which
leads to compact folded peptide conformations7). The resulting dense structures
strongly decrease the rate of enzymatic peptide hydrolysis, which is of significant
importance in the design of peptidomimetics [16]. Inhibitors of EFE (ethylene-forming
enzyme), amino transferase, tryptophane hydrolase, Dopa decarboxylase, histidine
decarboxylase, and carboxypeptidase are also found to contain this unique class of
ACCs [17].
In addition, (‡)-coronamic acid (8) [18], a subunit found in coronatine (9), is a
natural product isolated from Pseudomonas syringae, pv atropurpurea [19], which was
shown to induce the chlorosis of Italian rye grass leaves.
The presence of ACC subunits in nature along with its incorporation into bioactive
compounds has stimulated the interest for further development of synthetic method-
ologies to access them in enantiomerically enriched form. Numerous approaches have
been reported for the preparation of substituted ACCs [20], however, only a few
7
)
For recent incorporation of ACC into peptides, see [15].

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Helvetica Chimica Acta Vol. 85 (2002)
Scheme 2
EWG ˆ Electron withdrawing group, i.e., COOR, CN, NC, (PG)2N; PG ˆ protecting group.
methods allow the stereoselective preparation of all possible stereoisomers (Scheme 2)
[7][21].
Improvements on existing methodologies could provide a more direct synthesis of
ACC derivatives that avoids extensive functional-group differentiations and manipu-
lations. With this in mind, a direct incorporation of an −amino acid synthetic equivalent×
into an alkene via a transition metal catalyzed diazo decomposition appeared to be the
most effective way. We, thus, examined a number of possibilities, including imino,
phthalimido, and nitrodiazocarbonyl reagents as amine equivalents, which could be
quickly transformed to the desired amine [22]. A survey of the literature indicates that
precedents exist in cyclopropanation reactions involving a-nitro-a-diazocarbonyl
reagents (10) as −amino acid equivalents×8). The approach adopted by O×Bannon and
Dailey employs the decomposition of diazo compounds by [Rh(OAc)2]2 in the presence
of an alkene to afford substituted 1-nitrocyclopropanecarbonyls 11 (Scheme 3) [23].
Seebach and H‰ner showed that hydrogenation of 2 (R ˆ H) (ˆ11: R ˆ OR', R1 ˆ H),
followed by saponification provided 1 (ˆ12: R ˆ OH, R1 ˆ H) [9].
Surprisingly, there are relatively few reported examples of other nitrocarbenes in
the literature [24]. In this publication, we report on a more practical method for the
preparation of a-nitro-a-diazocarbonyl reagents 10, and we describe our efforts to
optimize the diastereoselectivity in the transition metal catalyzed cyclopropanation of
8
)
For transition metal catalyzed cyclopropanations, see [23].

Helvetica Chimica Acta Vol. 85 (2002)
4471
Scheme 3
alkenes with these reagents. Our ultimate goal will be to access either diastereoisomers
of 11 by varying the structure of the starting diazo reagent or of the catalyst. In the
second part, we describe the novel OÀH insertion of the corresponding metal a-
nitrocarbonylÀcarbene complexes.
Results and Discussion. Preparation of a-Nitro-a-diazo Carbonyl Reagents. To the
best of our knowledge, there are only two reports of the preparation of a-nitro-a-diazo
esters via a diazo-transfer process. Hendrickson and Wolf [25] showed that ethyl a-
nitro-a-diazoacetate can be prepared in 8% yield by mixing ethyl nitroacetate with 4-
(azidosulfonyl)benzoic acid. Alternatively, Balli and Lˆw showed that the use of
thiazolium azide 13 leads to a slightly more efficient diazo transfer reaction (Scheme 4)
[26].
Scheme 4
Schˆllkopf and co-workers developed a more efficient method of accessing a-nitro-
a-diazo esters and ketones involving the treatment of diazo compounds 14 with the
strong nitrating reagent N2O5 (Scheme 5) [24]. However, the preparation of N2O5 is
tedious since it decomposes above À308. Furthermore, two equivalents of the starting
diazo compound are required, the second being consumed when acting as a base to
deprotonate the intermediate diazonium ion.
Due to the inherent disadvantages associated with the existing methodologies, we
developed an improved procedure for the facile and general preparation of these
reagents. We previously reported [27] a novel diazo-transfer reaction involving the
treatment of a MeCN/hexanes solution of (trifluoromethyl)sulfonyl (trityl) azide [28]
and an a-nitro ester or ketone with pyridine, which affords the corresponding a-nitro-

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Helvetica Chimica Acta Vol. 85 (2002)
Scheme 5
a-diazo ester 17 and ketone 10 in high yields. The diazo transfer proceeds smoothly for
a large variety of alkyl substituents as a-nitro ester substrates 16 (Scheme 6), providing
the desired compounds in generally > 80% yield.
Scheme 6. Diazo-Transfer Reaction on a-Nitro Esters. Isolated yields after chromatography in parentheses.
Isolation of the a-nitro-a-diazo carbonyl compound from the reaction medium
involves simple concentration of the solvent under reduced pressure followed by flash
chromatography on silica gel with CHCl3 as eluent. The product elutes as a yellow band
and can be followed visually. Direct diazo transfer on nitroacetic acid is unsuccessful as
it decarboxylates in the presence of pyridine.
Under the same conditions, the diazo-transfer reaction also affords, in modest to
high yields, the corresponding a-nitro-a-diazo ketones 10a h starting from a-nitro
ketone 18 (Scheme 7). However, it was realized that the yields of the diazo-transfer
reaction could be substantially increased relative to those originially reported [27] by
addition of pyridine at 08 instead of room temperature. Presumably, the slight

Helvetica Chimica Acta Vol. 85 (2002)
4473
Scheme 7. Diazo-Transfer Reaction on a-Nitro Ketones. Yields in parentheses.
decomposition of the a-nitro ketone substrates in the presence of pyridine is reduced at
lower temperatures.
It should be mentioned that tert-butyl diazo ketone 10f decomposes at a moderate
rate (in 24 h) if not stored in the freezer9). The crystal structure of methyl a-nitro-a-
diazoacetate (17a) was obtained (Fig. 1)10).
Fig. 1. Chem 3D representation of the crystal structure of methyl diazonitroacetate (17a)
Cyclopropanation Reaction Catalyzed by Dirhodium Catalysts. Surprisingly, there
have been few reports of catalysts other than [Rh(OAc)2]2 for the cyclopropanation
reaction involving a-nitro-a-diazo carbonyl reagents. We were, thus, interested in
studying ligand effects on the diastereoselectivity and yield of the cyclopropanation
reaction for a given set of alkene/diazo reagents. A series of achiral dirhodium-based
catalysts were tested for their catalytic activity in a model system based on ethyl
9
)
a-Nitro-a-diazo carbonyl derivatives should be handled with great care due to their explosive nature. In
our hands, methyl ester 17a was found to be quite shock-sensitive.
For the X-ray crystal structure of a-nitro-a-diazoacetic acid, see [29].
10
)

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Helvetica Chimica Acta Vol. 85 (2002)
a-nitro-a-diazoacetate (17b) and styrene (Scheme 8). A variety of commercially
available dirhodium(II)carboxamidate catalysts including Rh2(cap)4 (Table 1, En-
try 1), Rh2((5R)-MEPY)4, Rh2((4S)-MEOX)4, and Rh2((4S)-MPPIM)4 were found to
lead only to decomposition or recovery of the diazo substrate under a variety of
conditions. [Rh((4S)-MEAZ)2]2 [30] proved to be an exception, and cyclopropanation
results with this catalyst have been previously reported by us in work involving
asymmetric cyclopropanations [31]. The focus then turned to various dirhodium(II)
carboxylate catalysts. An electron-withdrawing ligand (Table 1, Entry 2) was found to
give low yields of the corresponding cyclopropane 19 and a surprising recovery of 41%
of the diazo substrate. Sterically undemanding, electron-rich ligands (Entries 3 and 4)
were found to give higher yields of the desired cyclopropane. Further improvements in
the yields resulted with sterically demanding, electron-rich ligands (Entries 5 and 6). In
all cases, the trans-diastereoisomers were strongly favored.
Scheme 8
Table 1. Cyclopropanation Reaction with Dirhodium(II) Carboxamidates and Carboxylates
Entry
Catalyst
Yield of 19 [%]a)
cis/trans
b
1
2
3
4
5
6
[Rh(cap)2]2
)
dec.
24
79
76
84
[Rh(CF3CO2)2]2
[Rh(OAc)2]2
[Rh(C7H15CO2)2]2
[Rh(t-BuCO2)2]2
[Rh(Adaman)2]2
8 : 92
12 : 88
10 : 90
15 : 85
12 : 88
c
)
90
a) Combined yield (cis/trans) after column chromatography. b) cap: caprolactam. c) Adaman: adamantane-1-
carboxylate.
cis/trans-Selectivity as a Function of the Diazo Reagent. We then set out to study the
substituent effect of the a-nitro-a-diazocarbonyl substrate on the cis/trans selectivity.
We tested a number of cyclopropanation reactions with styrene as a substrate and
varied the size of the ester or ketone substituent (Scheme 9, Table 2).
Scheme 9

Helvetica Chimica Acta Vol. 85 (2002)
4475
Table 2. Diastereoselectivity as a Function of the Diazo Reagent
Entry
Product
R
Yield [%]a)
cis/trans
1
2
3
4
5
6
7
8
20a
20b
20c
20d
20e
20f
20g
20h
MeO
EtO
i-PrO
t-BuO
Me
Pr
Ph
t-Bu
78
80
78
81
9 : 91
12 : 88
25 : 75
45 : 55
22 : 78
19 : 81
84 : 16
80 : 20
77
74
74b)
55b)
a) Isolated yields after column chromatography. b) 15% (Entry 7) and 30% (Entry 8) yield of the corresponding
isoxazoline N-oxides resulting from cyclopropane opening were found as by-products.
A highly diastereoselective cyclopropanation favoring the trans-cyclopropanes 20
(the Ph group in 2-position is trans to the NO2 group) can be obtained when employing
a sterically minimally demanding group. With the methyl ester, a cis/trans-ratio of 9 :91
was obtained (Entry 1) while a cis/trans-ratio of 12 :88 was obtained with the ethyl ester
(Entry 2). Increasing alkyl-group steric bulk on the ester leads to loss of this
diastereoselectivity (Entries 3 and 4) resulting in almost equal preference of the two
diastereoisomers in the case of the tert-butyl ester (Entry 4). The use of moderately
bulky a-nitro-a-diazo ketones as substrates can produce a cis-selective product with cis/
trans-ratios of up to 84 :16 (Entry 7). These diastereoisomers can be readily separated
by column chromatography as is the case with the less-bulky esters. The absolute
configuration is in agreement with previously reported findings [23] and was further
confirmed by the crystal structure of trans-1-[2-(4-fluorophenyl)-1-nitro-cyclopropyl]-
ethanone.
It is also noteworthy to mention that increasing the steric bulk of the ketones
decreases the stability of the cyclopropanes. In the case of 1-adamantyl and cyclohexyl
derivatives, isolated yields ranged from 20 to 30%; most of the material was recovered
as the isoxazoline oxides after silica-gel chromatography (21, Scheme 10) [23].
Presumably, release of ring strain is the driving force of this rearrangement.
Scheme 10
Cyclopropanation of Various Alkenes. The cyclopropanation reaction is known to
proceed with a variety of alkenes (Scheme 11). It is generally believed that the highest
yields can be obtained with electron-rich, terminal, and cis-configured olefins (Table 3,
Entries 1 4). Surprisingly, however, when the cyclopropanation reaction was per-
formed with more-electron-deficient substrates such as 2-bromopropene and a-
bromostyrene (Entries 5 and 6), the corresponding cyclopropanes were afforded in

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Helvetica Chimica Acta Vol. 85 (2002)
modest yields11). b-Bromostyrene was also submitted to the same reaction conditions,
and the cyclopropanation afforded low yields suggesting the necessity for the
appropriate polarization in the substrate. Considering a concerted formation of the
nitrocyclopropanecarboxylate as proposed by Doyle et al. [33] for related systems, the
polarization of the b-bromostyrene would result in a destabilization of the intermedi-
ates, thus, decreasing cyclopropane formation.
Scheme 11
Table 3. Scope of Cyclopropanation with 17b
Entry
Alkene
Product
R1
R2
R3
Yield [%]
cis/trans
1
2
3
4
5
6
a-Methylstyrene
1,1-Diphenylethene
1H-Indene
1-Hexene
2-Bromopropene
a-Bromostyrene
22a
22b
22c
22d
22e
22f
Ph
Ph
H
Bu
Br
Br
Me
Ph
H
H
95
72 : 28a)
60b)
84
À2-CH2ÀC6H4À
97 : 3c)
40 : 60
80 : 20
75 : 25
H
H
H
H
40
50
77
Me
Ph
a) Cyclopropane/isoxazoline oxide. b) Yield of isoxazoline oxide c) exo/endo with respect to NO2.
Cyclopropane 22b completely rearranged to the corresponding isoxazoline oxide
on silica gel while the rearrangement of 22a was much slower. This effect probably
arises from the ability of the substituents to stabilize a partial positive charge in the
benzylic position. Accordingly, cyclopropanes 22c f were not found to show
rearrangement products. Strong electron-donating groups on an aryl ring can also
facilitate the rearrangement, thus, the cyclopropane resulting from the reaction with 4-
methoxystyrene gives only isoxazoline oxide when exposed to silica gel. The structure
of the cyclopropane 22c derived from the reaction with 1H-indene (Entry 3) was
confirmed by X-ray crystallography of the corresponding methyl ester showing the NO2
group exo to the ring as the predominant isomer (Fig. 2).
OÀH Insertions. As part of our continuing interest in the chemistry of a-nitro-a-
diazo carbonyl substrates, we wondered if they could potentially undergo OÀH-
insertion reactions, yielding the −novel× a-nitro-a-alkoxy carbonyl derivatives [34]. The
substrates 23 could then be reduced to serve as valuable precursors for alkoxy glycines
¬
[35]. Since the pioneering work of Teyssie and co-workers on the Rh-catalyzed
insertion of ethyl diazoacetate in the OÀH bond of alcohols [36], the use of Rh
catalysts has been largely investigated [5]. In a similar fashion, rhodium(II) acetate is
also an extremely effective catalyst for the novel conversion of these a-nitro-a-
11
)
For an ethyl diazoacetate cyclopropanation of a-fluorostyrene, see [32].

Helvetica Chimica Acta Vol. 85 (2002)
4477
Fig. 2. Chem 3D representation of the crystal structure of methyl exo-1,1a,6,6a-tetrahydro-1-nitrocyclopro-
pa[a]indene-1-carboxylate
diazocarbonyl substrates 10 or 17 into a-alkoxy-a-nitrocarbonyls 23 (Scheme 12). The
intermolecular OÀH-insertion reaction is possible with a range of primary to tertiary
alcohols (Table 4).
Scheme 12
Table 4. OÀH Insertion of Alcohols
Entry
Substrate
Product
R1
Yield [%]a)
1
2
3
4
5
6
7
8
9
17b
17b
17b
17b
17b
17h
17h
17h
10c
23a
23b
23c
23d
23e
23f
23g
23h
23i
H2CˆCHÀCH2
PhCH2
t-Bu
84
99
45
Cyclopropylmethyl
(R)-2-(Methoxycarbonyl)propyl
H2CˆCHÀCH2
PhCH2
87
74b)
92
84
Menthylc)
H2CˆCHÀCH2
79d)
78
a) Isolated yields after chromatography. b) Isolated as a 50 : 50 mixture of diastereoisomers. c) (1R,2S,5R)-
Menthyl. d) Isolated as a 55 : 45 mixture of diastereoisomers.
In the case of allyl alcohol, we did not observe any competing cyclopropanation
(Entries 1, 6, and 9) for substrates 17b, 17h, and 10c. The use of chiral alcohols such as
(À)-(1R,2S,5R)-menthol did not lead to high stereoinduction with a diastereoisomer
ratio of 55 :45 at the created a-center (Entry 8).
Due to the complete chemoselectivity with the allyl alcohol as a substrate we
decided to examine the relative rates of OÀH insertion vs. cyclopropanation in a
competition experiment (Scheme 13). Substrate 17b, styrene, and various alcohols

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Helvetica Chimica Acta Vol. 85 (2002)
were used to determine the relative rates of cyclopropanation products 20 vs. OÀH-
insertion products 23 (Table 5). The cyclopropanation of styrene is preferred over
OÀH insertion in the case of t-BuOH (Entry 1), while cyclopropanation and OÀH
insertion proceed at similar rates when styrene and i-PrOH are compared (Entry 2).
Finally, the OÀH-insertion pathway dominates when the primary PhCH2OH is used
(Entry 3). This behavior follows trends observed with ethyl diazoacetate.
Scheme 13
Table 5. OÀH Insertion vs. Cyclopropanation Competition Experiments
Entry
Product 23
R
Cyclopropanation/OÀH insertion
Yield of 20b ‡ 23 [%]a)
1
2
3
23c
23j
23b
t-Bu
i-Pr
PhCH2
10 : 1
1 : 1
1 : 4
77
78
94
a) Isolated yields after chromatography based on theoretical yield of product from crude ratios.
Conclusions.
In summary, the yields for the preparation of a-nitro-a-diazo
carbonyl substrates with trityl azide as a diazo-transfer reagent can be substantially
improved by simply cooling the reaction media to 08 during pyridine addition. The wide
range of substrates accessible by this method allowed us to effectively control the
diastereoselectivity in the cyclopropanation with styrene affording either cis- or trans-
diastereoisomers preferentially. The cyclopropanation occurs with modest to high
yields with a variety of alkene substrates including bromo alkenes, which are typically
low-yielding for other diazo derivatives.
A highly efficient method for the preparation of the novel a-alkoxy-a-nitro
carbonyl derivatives from the corresponding a-nitro-a-diazo carbonyl compounds by a
novel [Rh(OAc)2]2 catalyzed OÀH insertion with the desired alcohol is also reported.
The applications of these compounds are currently investigated and will be reported in
due course along with an improved method for enantioselective cyclopropanations.
Experimental Part
General. Unless otherwise mentioned, all reactions were carried out under Ar atmosphere with oven-dried
glassware. All solvents were dried on a GlassContour system (Irvine, CA). Pyridine was distilled from CaH2
while (trifluoromethyl)sulfonyl anhydride was distilled from P2O5. Column chromatography: flash chromatog-
raphy (FC) with the indicated solvent system on Silicycle silica-gel (230 400 mesh) according to the method of
Still et al. [37]. M.p.: Thomas-Hoover melting point apparatus, in open capillaries, uncorrected. IR: Perkin-
Elmer 783; only the most important and relevant frequencies are reported. 1H-NMR: Bruker AMX-300 or
AMX-R-400; at 400 MHz in CDCl3, if not stated otherwise; chemical shifts d in ppm from an internal standard
of residual CHCl3 (7.27 ppm); J in Hz. 13C-NMR: Bruker ARX-400; at 100 MHz in CDCl3, if not stated

Helvetica Chimica Acta Vol. 85 (2002)
4479
otherwise; chemical shifts d in ppm relative to the central line of the triplet at 77.23 ppm for CDCl3. Full
¬
assignment of chemical shifts was confirmed by DEPTexperiments. HR-MS: obtained from the Centre regional
¬
¬
¬
de spectrometrie de masse de l×Universite de Montreal; Kratos MS50; m/z. Combustion analyses were
¬ ¬
¬
¬
performed by the Laboratoire d×analyse elementaire of the Universite de Montreal.
Synthesis of a-Nitro Esters 16. Prepared according to the procedure reported by Mioskowski and co-
workers [38]. 16a and b are commercially available from Aldrich, 16d,e,h,p [38], 16k [39], 16l [31], 16c,g,i,m,n,r
[27] have been previously reported.
1,1-Dimethylallyl 2-Nitroacetate (16f): 334 mg (33%). Pale yellow oil. IR (film): 1751s, 1563s. 1H-NMR:
1.58 (s, 6 H); 5.09 (s, 2 H); 5.16 (d, J ˆ 10.4, 1 H); 5.24 (d, J ˆ 17.5, 1 H); 6.07 (dd, J ˆ 17.5, 10.9, 1 H). 13C-NMR:
26.3; 77.2; 85.3; 114.6; 140.7; 160.5. Anal. calc. for C7H11NO4 (173.17): C 48.55, H 6.40, N 8.09; found: C 48.55,
H 6.47, N 8.31.
Methyl (R)-2-Methyl-3-[(2-nitroacetyl)oxy]propanoate (16j): 150 mg (73%). Yellow oil. IR (film) 1760s,
1737s, 1567s, 1340s. 1H-NMR: 1.23 (d, J ˆ 7.2, 3 H); 2.86 (m, 1 H); 3.72 (s, 3 H); 4.35 (dd, J ˆ 10.9, 5.5, 1 H); 4.44
(dd, J ˆ 10.9, 7.4, 1 H); 5.17 (s, 2 H). 13C-NMR: 13.7; 38.8; 52.2; 67.8; 76.2; 161.8; 173.7.
(1S,2S,4R)-1,3,3-Trimethylbicyclo[2.2.1]hept-2-yl 2-Nitroacetate (16o): 283 mg (59%). Colorless oil. IR
(film): 1751s, 1565s. 1H-NMR: 0.81 (s, 3 H); 1.07 (s, 3 H); 1.12 (s, 3 H); 1.22 1.25 (m, 1 H); 1.44 1.77 (m, 6 H);
4.51 (s, 1 H); 5.20 (s, 2 H). 13C-NMR: 19.4; 20.1; 25.8; 26.5; 29.7; 39.9; 41.4; 48.3; 48.6; 76.5; 89.8; 162.3. HR-MS
‡
241.13176 (C12H19NO4 ; calc. 241.13141).
3-Bromopropyl 2-Nitroacetate (16q): 528 mg (75%). Pale yellow oil. IR (film): 1755s, 1563s. 1H-NMR: 2.24
(quint., J ˆ 6.2, 2 H); 3.45 (t, J ˆ 6.4, 2 H); 4.43 (t, J ˆ 6.0, 2 H); 5.19 (s, 2 H). 13C-NMR: 28.8; 31.3; 64.9; 76.3; 161.8.
Synthesis of the a-Nitro Ketones 18: Prepared according to the procedure reported by Baker and Putt for
18a,c,d,g [40], Simmons et al. for 18b [41], 18e,f [27], or Yuasa et al. for 18h [42].
3-Methyl-1-nitrobutan-2-one (18d): 1.26 g (59%). Clear, colorless oil. IR (film): 1732s, 1560s. 1H-NMR: 1.20
(d, J ˆ 6.9, 6 H); 2.72 (sept., J ˆ 6.9, 1 H); 5.38 (s, 2 H). 13C-NMR: 17.9; 39.8; 81.9; 199.8. HR-MS: 131.05819
‡
(C5H9NO3 ; calc. 131.05824).
1-(Adamant-1-yl)-2-nitroethanone (18g): 4.25 g (86%). White platelets. M.p. 828. IR (film): 1703s, 1547s.
1H-NMR: 1.69 1.86 (m, 11 H); 2.11 (br, 4 H); 5.44 (s, 2 H). 13C-NMR: 27.8; 27.9; 36.3; 36.4; 36.6; 37.9; 38.9;
‡
46.7; 80.1; 200.8. HR-MS: 223.12059 (C12H17NO3 ; calc. 223.12084).
Typical Procedure for the Preparation of the a-Nitro-a-diazo Carbonyls.
CAUTION: Although we have not experienced any problems in the handling of these compounds
((trifluoromethyl)sulfonyl azide and the a-nitro-a-diazo carbonyl derivatives), extreme care should be taken
when manipulating them due to their explosive nature.
Preparation of Trifluoromethylsulfonyl Azide Solution: According to Fritschi and Vasella [28].
Synthesis of a-Nitro-a-diazo Esters 17. Prepared according to the previously reported procedure in [27].
Compounds 17a e,g,i,l,m,n,p,r have been previously reported [27][31].
1,1-(Dimethyl)allyl 2-Diazo-2-nitroacetate (17f): 89 mg (73%). Yellow oil. IR (film): 2143s, 1744s, 1698s,
1515s, 1320s. 1H-NMR: 1.64 (s, 6 H); 5.19 (d, J ˆ 10.9, 1 H); 5.29 (d, J ˆ 17.4, 1 H); 6.13 (dd, J ˆ 17.4, 10.9, 1 H).
‡
13C-NMR: 26.6; 86.1; 114.8; 140.8; 154.1. HR-MS: 199.058979 (C7H9N3O4 ; calc. 199.059306).
Benzyl 2-Diazo-2-nitroacetate (17h): 98 mg (96%). Yellow oil. IR (film): 2149s, 1746s, 1703s, 1520s.
1H-NMR: 5.36 (s, 2 H); 7.40 (br., 5 H). 13C-NMR: 68.5; 101.8 (CN2); 128.9; 129.0; 129.3; 134.3; 155.5. HR-MS:
‡
221.043867 (C9H7N3O4 ; calc. 221.043656).
Methyl (R)-3-[(2-Diazo-2-nitroacetyl)oxy]-2-methylpropanoate (17j): 84 mg (68%). Yellow oil. IR (film):
2152s, 1741s, 1520s. 1H-NMR: 1.25 (d, J ˆ 7.2, 3 H); 2.86 2.92 (m, 1 H); 3.72 (s, 3 H); 4.94 4.47 (m, 2 H).
‡
13C-NMR: 13.6; 38.9; 52.2; 67.4; 101.7 (CN2); 155.1; 173.6. HR-MS: 232.05580 ([ M ‡ 1] , C7H9N3O6 ; calc.
232.05696).
(3-Methyloxetan-3-yl)methyl 2-Diazo-2-nitroacetate (17k): 114 mg (87%). Yellow oil. IR (film): 2150s,
1747s, 1703s, 1520s, 1323s. 1H-NMR: 1.32 (s, 3 H); 4.37 (s, 2 H); 4.39 (s, 2 H); 4.44 (s, 1 H); 4.46 (s, 1 H).
13C-NMR: 20.9, 39.3; 70.7; 79.2; 102.0 (CN2); 155.6.
(1S,2S,4R)-1,3,3-Trimethylbicyclo[2.2.1]heptan-2-yl 2-Diazo-2-nitroacetate (17o): 179 mg (96%). Yellow
solid. M.p. 468. IR (solid): 2145s, 1748s, 1698s, 1522s, 1323s. 1H-NMR: 0.83 (s, 3 H); 1.08 (s, 3 H); 1.13 (s, 3 H);
1.15 1.17 (m, 1 H); 1.23 1.27 (m, 1 H); 1.55 1.45 (m, 1 H); 1.79 1.60 (m, 4 H); 4.59 (d, J ˆ 1.9, 1 H).
13C-NMR: 19.4; 20.3; 25.8; 26.6; 29.6; 39.8; 41.3; 48.2; 48.6; 89.8; 101.8 (CN2); 155.9.
3-Bromopropyl 2-Diazo-2-nitroacetate (17q): 170 mg (99%). Yellow oil. IR (film): 2148s, 1746s, 1705s,
1
1515s, 1322s. H-NMR: 2.24 (quint., J ˆ 6.3, 2 H); 3.45 (t, J ˆ 6.3, 2 H); 4.44 (t, J ˆ 6.0, 2 H). 13C-NMR: 29.0;
31.3; 64.7; 101.8 (CN2); 155.4.

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Helvetica Chimica Acta Vol. 85 (2002)
Synthesis of a-Nitro-a-diazo Ketones 10: Typical procedure according to [27], except that the mixture was
cooled in an ice bath (at 08) before a slow, dropwise addition of pyridine. The soln. was allowed to warm slowly
to r.t. overnight, concentrated, and purified by FC (SiO2; CHCl3). Compounds 10c,e,f have been previously
reported [27].
1-Diazo-1-nitropropan-2-one (10a): 146 mg (83%). Pale yellow solid. M.p. 428. IR (solid): 2163s, 1656s,
1497s, 1276s. 1H-NMR: 2.66 (s, 3 H). 13C-NMR: 29.2; 112.6 (CN2); 184.4. (Note: this product readily sublimes in
vacuo).
1-Diazo-1-nitropentan-2-one (10b): 112 mg (81%). Pale yellow solid. M.p. 36 378. IR (solid): 2150s, 1664s,
1497s, 1310s. 1H-NMR: 0.97 (t, J ˆ 7.4, 2 H); 1.68 (m, 2 H); 2.96 (t, J ˆ 7.3, 2 H). 13C-NMR: 13.7; 17.2; 42.8; 112.3
(CN2); 187.0.
1-Diazo-3-methyl-1-nitrobutan-2-one (10d): 259 mg (93%). Yellow oil. IR (film): 2170s, 2136s, 1666s, 1513s,
1313s. 1H-NMR: 1.20 (d, J ˆ 6.8, 6 H); 3.67 (sept., J ˆ 6.8, 1 H). 13C-NMR: 18.2; 37.8; 191.2. HR-MS: 157.04927
‡
(C5H7N3O3 ; calc. 157.04874).
1-(Adamant-1-yl)-2-diazo-2-nitroethanone (10g): 139 mg (93%). Yellow solid. M.p. 64 658. IR (solid):
2164s, 1638s, 1495s, 1268s. 1H-NMR: 1.77 (br., 6 H); 2.03 (br., 6 H); 2.10 (br., 3 H). 13C-NMR: 28.1; 36.4; 36.6;
47.8; 115.0 (CN2); 190.5.
tert-Butyl N-(3-Diazo-1-benzyl-3-nitro-2-oxopropyl)carbamate (10h): 114 mg (80%). Pale yellow solid.
M.p. 1288 (dec.). IR (solid): 2131s, 1684s, 1510s, 1309s. 1H-NMR: 1.38 (s, 9 H); 2.75 2.81 (m, 1 H); 3.19 3.24
(m, 1 H); 5.04 (d, J ˆ 8.3, 1 H); 5.54 5.59 (m, 1 H); 7.23 7.36 (m, 5 H). 13C-NMR: 28.4; 37.7; 58.0; 80.7; 113.3;
127.6; 129.0; 129.5; 135.3; 155.3; 186.4.
Cyclopropanations with 10 or 17. In a round-bottomed flask was added the appropriate catalyst (2 mol-%
based on diazo compound). Freshly distilled alkene (5 equiv.) was added, then, the a-nitro-a-diazo carbonyl
compound (0.50 mmol, 1 equiv.) in distilled CH2Cl2 (0.5 ml, 1.0m) was added via syringe ensuring a controlled
rate of N2 evolution. The soln. was stirred for 4 h, concentrated under reduced pressure, and purified by FC
(SiO2; hexanes/AcOEt 97:3) to yield the cyclopropanes.
Catalysts. [Rh(OAc)2]2 and [Rh(cap)2]2 were purchased from Aldrich, while [Rh(CF3CO2)2]2 and
[Rh(C7H15CO2)2]2 were purchased from Strem Chemicals. [Rh(Me3CO2)2]2 and [Rh(Adaman)2]2 were prepared
according to known procedures [43][44]. Cyclopropanes 19, 20a,b,d,g have been previously reported [31].
Isopropyl cis- and trans-1-Nitro-2-phenylcyclopropane-1-carboxylate (20c): 97 mg (78%, cis/trans 25 :75).
Clear, colorless oil.
Data of trans-20c. IR (film): 1739s, 1545s, 1351s. 1H-NMR: 0.82 (d, J ˆ 6.3, 3 H); 1.02 (d, J ˆ 6.3, 3 H); 2.18
(dd, J ˆ 10.7, 6.6, 1 H); 2.44 (dd, J ˆ 9.1, 6.6, 1 H); 3.76 (t, J ˆ 9.7, 1 H); 4.81 (sept., J ˆ 6.3, 1 H); 7.20 7.33 (m,
5 H). 13C-NMR: 20.6; 21.15; 21.21; 34.1; 70.8; 72.0; 128.4; 128.6; 128.7; 132.3; 161.5. HR-MS: 249.10065
‡
(C13H15NO4 ; calc. 249.10011).
Data of cis-20c: 1H-NMR: 1.33 (dd, J ˆ 6.3, 4.8, 6 H); 2.00 (dd, J ˆ 9.9, 6.9, 1 H); 2.44 (dd, J ˆ 9.1, 6.6, 1 H);
3.46 (dd, J ˆ 9.8, 9.3, 1 H); 5.20 (sept., J ˆ 6.3, 1 H); 7.21 7.37 (m, 5 H). 13C-NMR: 20.7; 21.7; 21.8; 33.6; 71.7;
73.0; 128.5; 128.8; 128.9; 131.7; 165.0. Anal. calc. for C13H15NO4 (249.27): C 62.64, H 6.07, N 5.62; found: C 62.47,
H 6.15, N 5.62.
cis- and trans-1-(1-Nitro-2-phenylcyclopropyl)ethan-1-one (20e): 159 mg (77%, cis/trans 22 :78). White
solid.
Data of trans-20e: M.p. 67 698. IR (solid): 1707s, 1528s, 1351s. 1H-NMR: 2.09 (s, 3 H); 2.21 (dd, J ˆ 10.6,
6.4, 1 H); 2.58 (dd, J ˆ 9.0, 6.4, 1 H); 3.82 (t, J ˆ 9.9, 1 H); 7.13 7.15 (m, 2 H); 7.29 7.32 (m, 3 H). 13C-NMR:
‡
20.3; 29.1; 37.2; 77.1; 128.5; 128.6; 129.0; 131.3; 193.7. HR-MS: 205.074398 (C11H11NO3 ; calc. 205.073893).
Data of cis-20e: IR (film): 1707s, 1533s, 1357s. 1H-NMR: 2.02 (dd, J ˆ 9.8, 6.4, 1 H); 2.52 (s, 3 H); 2.73 (dd,
J ˆ 9.3, 6.5, 1 H); 3.56 (t, J ˆ 9.5, 1 H); 7.19 7.21 (m, 2 H); 7.30 7.34 (m, 3 H). 13C-NMR: 22.8; 27.8; 36.9; 84.3;
128.7; 128.87; 128.9; 131.6; 197.3. Anal. calc. for C11H11NO3 (205.22): C 64.38, H 5.40, N 6.83; found: C 64.16,
H 5.45, N 6.70.
cis- and trans-1-(1-Nitro-2-phenylcyclopropyl)butan-1-one (20f): 113 mg (74%, cis/trans 19 :81). Clear,
colorless oil, inseparable cis/trans-mixture. IR (film): 1716s, 1535s, 1349s.
1
Data of trans-20f: H-NMR: 0.62 (t, J ˆ 7.4, 3 H); 1.12 1.20 (m, 2 H); 1.35 1.39 (m, 2 H); 2.17 (dd, J ˆ
10.6, 6.4, 1 H); 2.68 (dd, J ˆ 6.4, 4.4, 1 H); 3.81 (t, J ˆ 9.9, 1 H); 7.12 7.14 (m, 2 H); 7.26 7.33 (m, 3 H).
‡
13C-NMR: 13.4; 17.0; 20.1; 36.7; 43.5; 77.1; 128.6; 128.9; 131.4; 196.3. HR-MS233.10524 (C 13H15NO3
:
233.10519).
Data of cis-20f: 1H-NMR: 0.96 (t, J ˆ 7.4, 3 H); 1.65 1.75 (m, 1 H); 2.75 2.83 (m, 2 H); 2.90 3.05 (m,
1 H); 3.56 (t, J ˆ 9.5, 1 H); 7.19 7.21 (m, 2 H); 7.26 7.33 (m, 3 H). 13C-NMR: 13.7; 17.5; 22.5; 36.1; 41.6; 80.1;
128.7; 128.8; 129.2; 131.8; 199.5.

Helvetica Chimica Acta Vol. 85 (2002)
4481
cis- and trans-2,2-Dimethyl-1-(1-nitro-2-phenylcyclopropyl)propan-1-one (20h): 148 mg (55%, cis/trans
80 :20). White solid, inseparable cis/trans-mixture. M.p. 48 508. IR (solid): 1705s, 1539s.
Data of trans-20h: 1H-NMR: 0.82 (s, 9 H); 1.98 (dd, J ˆ 10.7, 6.5, 1 H); 2.54 (dd, J ˆ 9.2, 6.5, 1 H); 3.86 (t,
J ˆ 9.3, 1 H); 7.09 7.12 (m, 1 H); 7.39 7.24 (m, 4 H). 13C-NMR: 20.2; 27.2; 34.8; 44.9; 76.6; 128.5; 128.6; 128.9;
131.7; 202.4.
Data of cis-20h: IR (film): 1705s, 1533s. 1H-NMR: 1.31 (s, 9 H); 1.71 (dd, J ˆ 9.8, 6.8, 1 H); 2.76 (dd, J ˆ 9.4,
6.8, 1 H); 3.55 (t, J ˆ 9.6, 1 H); 7.09 7.12 (m, 1 H); 7.24 7.39 (m, 4 H). 13C-NMR: 20.2; 28.2; 31.7; 46.2; 76.7;
‡
128.5; 128.7; 129.0; 131.8; 203.2. HR-MS: 247.121697 (C14H17NO3 ; calc. 247.120844). Anal. calc. for C14H17NO3
(247.30): C 68.00, H 6.93, N 5.66; found: C 68.27, H 7.06, N 5.70.
Ethyl 2-Methyl-1-nitro-2-phenylcyclopropane-1-carboxylate (22a): 118 mg (95%). White solid, as a
cyclopropane/isoxazoline oxide mixture (78 :28) after chromatography.
Data of cis-22a: M.p. 54 558. IR (film): 1736s, 1543s. 1H-NMR: 0.89 (t, J ˆ 7.1, 3 H); 1.54 (s, 3 H); 2.15 (d,
J ˆ 6.8, 1 H); 2.42 (d, J ˆ 6.8, 1 H); 3.89 3.95 (m, 2 H); 7.26 7.35 (m, 5 H). 13C-NMR: 13.7; 25.1; 26.5; 39.4;
‡
62.7; 76.4; 127.9; 128.0; 128.8; 139.3; 163.8. HR-MS250.106823 (C 13H15NO4 : calc. 250.107933).
Data of 4,5-Dihydro-5-methyl-5-phenylisoxazole-3-carboxylic Acid Ethyl Ester 2-Oxide: IR (film): 1723s,
1
1606s. H-NMR: 1.32 (t, J ˆ 7.1, 3 H); 1.82 (s, 3 H); 3.57 (m, 2 H); 4.29 (q, J ˆ 7.2, 2 H); 7.45 7.33 (m, 5 H).
13C-NMR: 14.4; 28.3; 44.5; 62.0; 82.9; 109.1; 124.3; 128.4; 129.1; 143.1; 159.2.
Ethyl 1-Nitro-2,2-diphenylcyclopropane-1-carboxylate (22b): Observed in the crude reaction mixture.
1H-NMR: 0.98 (t, J ˆ 7.2, 3 H); 2.67 (d, J ˆ 6.9, 1 H); 3.01 (d, J ˆ 6.9, 1 H); 3.98 4.08 (m, 2 H); 7.31 7.45 (m,
10 H). After FC (SiO2), 4,5-dihydro-5,5-diphenyl-isoxazole-3-carboxylic acid ethyl ester 2-oxide was obtained
(64 mg, 60%). Pale yellow solid. M.p. 101 1038. IR (solid): 1731s, 1620s. 1H-NMR: 1.33 (dt, J ˆ 7.1, 0.6, 3 H);
4.04 (s, 2 H); 4.30 (dq, J ˆ 7.1, 0.6, 2 H); 7.31 7.45 (m, 10 H). 13C-NMR: 14.4; 43.8; 62.2; 86.0; 109.0; 125.9;
‡
128.7; 129.0; 141.6; 159.1. HR-MS: 312.123909 (C18H17NO4 ; calc. 312.123583). Anal. calc. for C18H17NO4
(311.33): C 69.44, H 5.50, N 4.50; found: C 69.63, H 5.53, N 4.37.
Ethyl exo- and endo-1,1a,6,6a-Tetrahydro-1-nitrocyclopropa[a]indene-1-carboxylate (22c): 120 mg (84%,
exo/endo 97:3). White solid.
1
Data of exo-22c: M.p. 57 588. IR (film): 1739s, 1539s, 1338s. H-NMR: 0.82 (dt, J ˆ 7.1, 0.26, 3 H); 3.12
(ddd, J ˆ 7.3, 6.2, 0.9, 1 H); 3.40 (dd, J ˆ 18.0, 6.1, 1 H); 3.49 (d, J ˆ 18.0, 1 H); 3.82 (d, J ˆ 7.4, 1 H); 3.85 3.92
(m, 2 H); 7.15 7.26 (m, 3 H); 7.42 7.44 (m, 1 H). 13C-NMR: 13.5; 34.4; 42.0; 62.3; 72.9; 125.1; 126.0; 127.5;
‡
128.3; 137.9; 142.0; 160.5. HR-MS: 247.084385 (C13H13NO4 ; calc. 247.084458). Anal. calc. for C13H13NO4
(247.08): C 63.15, H 5.30, N 5.67; found: C 63.11, H 5.30, N 5.65.
Data of endo-22c: 1H-NMR: 1.31 (t, J ˆ 7.1, 3 H); 2.94 (dt, J ˆ 7.1, 1.6, 1 H); 4.33 (q, J ˆ 7.2, 2 H); 7.21 7.49
(m, 4 H).
Ethyl cis- and trans-2-butyl-1-nitrocyclopropane-1-carboxylate (22d): 38 mg (40%, cis/trans 40 :60). Clear,
colorless oil, inseparable cis/trans-mixture. IR (film): 1742s, 1545s.
Data of trans-22d: 1H-NMR: 0.88 (t, J ˆ 7.3, 3 H); 1.14 1.53 (m, 10 H); 1.63 1.70 (m, 2 H); 1.81 1.88 (m,
2 H); 2.37 2.44 (m, 2 H); 4.32 (q, J ˆ 7.2, 2 H). 13C-NMR: 14.2; 22.3; 22.6; 23.3; 27.7; 28.1; 30.6; 62.9; 70.7;
163.8.
Data of cis-22d: 1H-NMR: 0.89 (t, J ˆ 7.3, 3 H); 1.14 1.53 (m, 10 H); 2.08 2.14 (m, 2 H); 4.29 (m, 2 H).
‡
13C-NMR: 14.0; 14.1; 22.3; 22.4; 23.3; 29.5; 30.8; 63.1; 71.7; 163.8. HR-MS: 216.123199 (C10H17NO4 ; calc.
216.123583). Anal. calc. for C10H17NO4 (215.24): C 55.80, H 7.96, N 6.51; found: C 55.79, H 8.08, N 6.41.
Ethyl cis- and trans-2-bromo-2-methyl-1-nitrocyclopropane-1-carboxylate (22e): 62 mg (50%, cis/trans
20 :80). Clear, colorless oil, inseparable cis/trans-mixture. IR (film): 1745s, 1552s.
Data of trans-22e: 1H-NMR: 1.34 (t, J ˆ 7.1, 3 H); 1.94 (s, 3 H); 2.21 (d, J ˆ 8.6, 1 H); 2.37 (d, J ˆ 8.6, 1 H);
4.35 (q, J ˆ 7.1, 2 H ) . 13C-NMR: 14.2; 27.0; 30.6; 34.4; 63.9; 74.5; 162.1.
1
Data of cis-22e: H-NMR: 1.32 (t, J ˆ 7.2, 3 H); 2.06 (s, 3 H); 2.12 (d, J ˆ 8.7, 1 H); 2.49 (d, J ˆ 8.7, 1 H);
4.30 (q, J ˆ 7.1, 2 H ) . 13C-NMR: 14.1; 24.9; 31.4; 36.2; 63.8; 76.9; 163.0. Anal. calc. for C7H10BrNO4 (252.07):
C 33.35, H 4.00, N 5.56; found: C 33.39, H 4.04, N 5.48.
Ethyl cis- and trans-2-bromo-1-nitro-2-phenylcyclopropane-1-carboxylate (22f): 160 mg (77%, cis/trans
75 :25). Pale yellow solid.
Data of trans-22f: Clear, colorless oil. IR (film): 1746s, 1554s. 1H-NMR: 1.44 (t, J ˆ 7.2, 3 H); 2.59 (d, J ˆ
8.7, 1 H); 3.03 (d, J ˆ 8.8, 1 H); 4.48 (q, J ˆ 7.2, 2 H); 7.34 7.39 (m, 3 H); 7.45 7.48 (m, 2 H). 13C-NMR: 14.2;
28.9; 39.7; 63.9; 74.5; 128.8; 129.1; 130.0; 134.2; 161.6.
1
Data of cis-22f: Yellow solid. M.p. 79 808. IR (film): 1732s, 1548s. H-NMR (300 MHz): 0.93 (t, J ˆ 7.1,
3 H); 2.75 (d, J ˆ 8.7, 1 H); 2.83 (d, J ˆ 8.7, 1 H); 3.95 3.99 (m, 2 H); 7.35 7.37 (m, 3 H); 7.44 7.46 (m, 2 H).
13C-NMR (75 MHz): 13.6; 29.5; 39.4; 63.5; 75.1; 128.6; 129.0; 129.6; 137.2; 161.7. HR-MS: 312.995537

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Helvetica Chimica Acta Vol. 85 (2002)
‡
(C12H12BrNO4 ; calc. 312.994969). Anal. calc. for C12H12BrNO4 (314.14): C 45.88, H 3.85, N 4.46; found:
C 45.99, H 3.86, N 4.51.
Synthesis of a-Alkoxy-a-nitro Carbonyl Compounds. Typical Procedure. To a mixture of rhodium(II)
acetate (8.8 mg 5.0 mol-%) and the alcohol (2.5 mmol, 5 equiv.) was added dropwise a soln. of the a-nitro-a-
diazo ester (0.5 mmol, 1 equiv.) in dry CH2Cl2 (0.50 ml, 1.0m). The mixture was stirred for 2 4 h at 208,
concentrated under reduced pressure, and purified by FC (SiO2; hexanes/AcOEt 95 :5).
Ethyl 2-(Allyloxy)-2-nitroacetate (23a): 74 mg (84%). Clear, colorless oil. IR (film): 1760s, 1575s. 1H-NMR:
1.33 (t, J ˆ 7.1, 3 H); 4.21 4.26 (m, 1 H); 4.33 (q, J ˆ 7.1, 2 H); 4.48 4.53 (m, 1 H); 5.38 5.44 (m, 2 H); 5.60 (s,
1 H); 5.89 5.98 (m, 1 H). 13C-NMR: 14.0; 63.8; 73.9; 103.3; 121.8; 131.0; 161.7.
Ethyl 2-(Benzyloxy)-2-nitroacetate (23b): 97 mg (99%). Clear, colorless oil. IR (film): 1760s, 1575s.
1H-NMR: 1.31 (t, J ˆ 7.1, 3 H); 4.31 (q, J ˆ 7.1, 2 H); 4.73 (d, J ˆ 11.6, 1 H); 5.06 (d, J ˆ 11.6, 1 H); 5.59 (s, 1 H);
7.38 7.42 (m, 5 H). 13C-NMR: 14.0; 63.8; 74.6; 103.2; 129.0; 129.1; 129.4; 134.0; 161.6. Anal. calc. for C11H13NO5
(239.04): C 55.23, H 5.48, N 5.86; found: C 55.25, H 5.52, N 5.88.
Ethyl 2-(tert-Butoxy)-2-nitroacetate (23c): 38 mg (45%). Clear, colorless oil. IR (film): 1760s, 1575s.
1H-NMR: 1.30 (t, J ˆ 7.2, 3 H); 1.32 (s, 9 H); 4.29 (dq, J ˆ 1.3, 7.2, 2 H); 5.73 (s, 1 H). 13C-NMR: 14.0; 27.5; 63.6;
81.6; 100.0; 163.1.
Ethyl 2-(Cyclopropylmethoxy)-2-nitroacetate (23d): 83 mg (87%). Clear, colorless oil. IR (film): 1760s,
1574s. 1H-NMR: 0.28 0.35 (m, 2 H); 0.62 0.68 (m, 2 H); 1.15 1.19 (m, 1 H); 1.33 (t, J ˆ 7.1, 3 H); 3.65 3.70
(m, 2 H); 4.33 (q, J ˆ 7.1, 2 H); 5.68 (s, 1 H). 13C-NMR: 3.3; 3.9; 9.8; 14.0; 63.8; 78.3; 104.2; 161.9.
Methyl (2R)-3-[(Ethoxycarbonyl)(nitro)methoxy]-2-methylpropanoate (23e): 125 mg (74%) as a ca. 50 :50
mixture of diastereoisomers. Clear, colorless oil. IR (film): 1742s, 1576s, 1463s. 1H-NMR: 1.25 (d, J ˆ 7.2, 3 H);
1.30 (d, J ˆ 7.2, 3 H); 1.344 (t, J ˆ 7.1, 3 H); 1.338 (t, J ˆ 7.1, 3 H); 2.87 2.98 (m, 1 H); 3.74 (s, 3 H); 3.87 3.99
(m, 1 H); 4.02 4.06 (m, 0.5 H); 4.16 4.21 (m, 0.5 H); 4.32 4.36 (m, 2 H); 5.624 (s, 1 H); 5.629 (s, 1 H).
13C-NMR: 13.8; 14.0; 39.8; 40.0; 52.2; 63.70; 63.74; 74.7; 74.9; 104.7; 105.0; 161.4; 161.5; 173.9; 174.3.
Benzyl 2-(Allyloxy)-2-nitroacetate (23f): 92 mg (92%). Clear, colorless oil. IR (film): 1760s, 1573s.
1H-NMR: 4.21 4.26 (m, 1 H); 4.48 4.53 (m, 1 H); 5.29 (s, 2 H); 5.37 5.42 (m, 2 H); 5.64 (s, 1 H); 5.87 5.97
(m, 1 H); 7.33 7.41 (m, 5 H). 13C-NMR: 69.1; 73.9; 103.1; 121.7; 128.6; 128.9; 129.1; 130.9; 134.1; 161.6.
Benzyl 2-(Benzyloxy)-2-nitroacetate (23g): 101 mg (84%). Clear, colorless oil. IR (film): 1761s, 1574s.
1H-NMR: 4.73 (d, J ˆ 11.6, 1 H); 5.06 (d, J ˆ 11.6, 1 H); 5.26 (s, 2 H); 5.62 (s, 1 H); 7.31 7.41 (m, 10 H).
13C-NMR: 69.0; 74.7; 103.2; 128.5; 128.7; 128.8; 128.9; 129.0; 129.3; 134.0; 134.1; 161.5.
Benzyl 2-[(1R,2S,5R)-Menthyloxy]-2-nitroacetate (23h): 110 mg (79%) as 55 :45 mixture of diastereoisom-
1
ers. Clear, colorless oil. M.p. 40 428. IR (film): 1745s, 1571s. H-NMR: 0.77 (d, J ˆ 6.9, 6 H); 0.86 (d, J ˆ 7.0,
6 H); 0.85 0.94 (m, 20 H); 1.00 1.14 (m, 2 H); 1.26 1.49 (m, 6 H); 1.60 1.72 (m, 6 H); 1.90 2.12 (m, 4 H);
2.43 2.47 (m, 1 H); 3.50 3.58 (m, 2 H); 5.22 5.32 (m, 4 H); 5.64 (s, 1 H); 5.78 (s, 1 H); 7.31 7.41 (m, 10 H).
13C-NMR: 15.9; 16.0; 20.9; 21.2; 22.2; 22.3; 23.0; 23.1; 25.4; 25.5; 31.6; 31.8; 34.0; 34.1; 39.3; 40.4; 40.5; 47.8; 48.1;
68.8; 69.0; 82.4; 87.3; 102.0; 105.4; 128.5; 128.7; 128.9; 129.0; 129.1; 134.2; 134.3; 162.26; 162.31. Anal. calc. for
C19H27NO5 (349.42): C 65.31, H 7.79, N 4.01; found: C 65.61, H 8.05, N 3.95.
1-(Allyloxy)-1-nitro-2-phenylethan-2-one (23i): 86 mg (78%). Pale yellow oil. IR (film): 1700s, 1574s.
1H-NMR: 4.33 4.38 (m, 1 H); 4.58 4.63 (m, 1 H); 5.40 5.45 (m, 2 H); 5.94 6.04 (m, 1 H); 6.20 (s, 1 H); 7.48
7.52 (m, 2 H); 7.63 7.67 (m, 1 H); 7.97 7.99 (m, 2 H). 13C-NMR: 74.3; 106.4; 121.9; 129.2; 129.7; 131.0; 132.6;
135.1; 185.9. Anal. calc. for C11H11NO4 (221.22): C 59.73, H 5.01, N 6.33; found: C 59.45, H 4.99, N 6.25.
Ethyl 2-(Isopropoxy)-2-nitroacetate (23j): 413 mg (72%). Clear, colorless oil. IR (film): 1761s, 1575s.
1H-NMR: 1.25 1.38 (m, 9 H); 3.99 (sept., J ˆ 7.1, 1 H) 4.32 (q, J ˆ 7.1, 2 H); 5.61 (s, 1 H). 13C-NMR: 14.3; 21.6;
22.7; 64.0; 76.9; 103.8; 162.7. Anal. calc. for C7H13NO5 (191.19): C 43.98, H 6.85, N 7.33; found: C 43.99, H 6.82,
N 7.24.
X-Ray Crystal-Structure Analyses of 17a and the Methyl Ester Derivative of 22c. The intensities of both
crystals were collected on a Nonius CAD-4 diffractometer with CuKa radiation (l ˆ 1.54056 ä) and w/2q scan.
The structures were solved by direct methods and refined on F2(SHELXL96). H-atoms were treated as riding.
Crystals of 17a were grown from a CHCl3 soln. They were orthorhombic, C1.5H1.5N1.5O2, Mr 72.542 g molÀ1
,
crystal size 0.49  0.48  0.38 mm, space group P212121, a ˆ 13.322(2) ä, b ˆ 5.949(2) ä, c ˆ 7.364(2) ä, Vˆ
583.6(3) ä3, Z ˆ 8; Dx ˆ 1.6512 Mg mÀ3, No. of reflections measured ˆ 4240, observed ˆ 611 (I > 2s(I)),
intensity decay ˆ 7.3%, qmax ˆ 69.848, No. of refined parameters ˆ 63, R factorˆ 0.0406, wR ˆ 0.1016, S ˆ 1.052,
diff. densitymax ˆ 0.268 e äÀ3, diff. densitymin ˆ À0.154 e äÀ3
.
Crystals of methyl exo-1,1a,6,6a-tetrahydro-1-nitrocyclopropa[a]indene-1-carboxylate were grown from an
AcOEt/hexanes soln. They were monoclinic, C12H11NO4, Mr 233.218 g molÀ1, crystal size 0.20 Â 0.14 Â 0.05 mm,
space group P212121, a ˆ 10.026(3) ä, b ˆ 14.221(5) ä, c ˆ 8.566(3) ä, V ˆ 1136.4(7) ä3, Z ˆ 4; Dx ˆ 1.3631 Mg

Helvetica Chimica Acta Vol. 85 (2002)
4483
mÀ3, No. of reflections measured ˆ 16427, observed ˆ 2159 (I > 2s(I)), intensity decay ˆ 14.0%, qmax ˆ 69.828,
No. of refined parameters ˆ 156, R factorˆ 0.0387, wR ˆ 0.0816, S ˆ 0.726, diff. densitymax ˆ 0.160 e äÀ3, diff.
densitymin ˆ À0.146 e äÀ3
.
Supplementary crystallographic data has been deposited with the Cambridge Crystallographic Data Centre
as deposition Nos.: CCDC-189718 (17a) and -189717 (methyl exo-1,1a,6,6a-tetrahydro-1-nitrocyclopropa[a]in-
dene-1-carboxylate). Copies of the data can be obtained, free of charge, on application to the CCDC, 12 Union
Road, Cambridge CB21EZ UK (fax: ‡ 44(1223)336033; e-mail: deposit@ccdc.com.ac.uk).
This work was supported by NSERC (Canada) (R. W.), Merck Frosst, Boehringer Ingelheim (Canada) Ltd.,
¬
¬
¬
¬
and the Universite de Montreal. We are also grateful to Francine Belanger-Gariepy for solving the X-ray crystal
structures.
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Received July 25, 2002