Synthesis of amido-spiro[2.2]pentanes via Simmons-Smith cyclopropanation of allenamides

Article abstract of DOI:10.1039/b908205k

A detailed account of Simmons-Smith cyclopropanations of allenamides en route to amido-spiro[2.2]pentanes is described here. While the diastereoselectivity was low when using unsubstituted allenamides, the reaction is overall efficient and general, representing the most direct synthesis of both chemically and biologically interesting amido-spiro[2.2]pentane systems. With α-substituted allenamides, while the diastereoselectivity could be improved significantly based on a series of conformational analyses, both mono- and bis-cyclopropanation products were observed. Consequently, several structurally intriguing amido-methylene cyclopropanes could also be prepared. The Royal Society of Chemistry 2009.

Full text of DOI:10.1039/b908205k

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Synthesis of amido-spiro[2.2]pentanes via Simmons–Smith cyclopropanation
of allenamides†
Ting Lu, Ryuji Hayashi, Richard P. Hsung,* Kyle A. DeKorver, Andrew G. Lohse, Zhenlei Song and Yu Tang
Received 27th April 2009, Accepted 19th May 2009
First published as an Advance Article on the web 19th June 2009
DOI: 10.1039/b908205k
A detailed account of Simmons–Smith cyclopropanations of allenamides en route to
amido-spiro[2.2]pentanes is described here. While the diastereoselectivity was low when using
unsubstituted allenamides, the reaction is overall efficient and general, representing the most direct
synthesis of both chemically and biologically interesting amido-spiro[2.2]pentane systems. With
a-substituted allenamides, while the diastereoselectivity could be improved significantly based on a
series of conformational analyses, both mono- and bis-cyclopropanation products were observed.
Consequently, several structurally intriguing amido-methylene cyclopropanes could also be prepared.
Despite these biological interests, and despite a number of
elegant approaches toward spiro[2.2]pentanes in literature, the
overall synthetic effort toward amino-spiro[2.2]pentanes has
Introduction
Spiro[2.2]pentanes,1 the smallest members of the triangulane
been limited.2,13 Few involve direct bis-cyclopropanations of
allenes,14 with many adopting mono-cyclopropanations of methy-
lene cyclopropanes prepared through other means.15 To the
best of our knowledge, preparation of amino-spiro[2.2]pentanes
directly through bis-cyclopropanations of 1-amino-allenes is
not known.2,10–13,16 Our recent interest17,18 in cyclopropana-
tions of enamides13,19,20 en route to optically enriched amino-
cyclopropanes21,22 coupled with our decade long efforts in devel-
oping the chemistry of allenamides23–26 allowed us to envision
the possibility of developing a direct construction of amido-
spiro[2.2]pentanes via Simmons–Smith cyclopropanation of al-
lenamides 1 [Scheme 1]. Based on our previous work on a number
of different stereoselective cycloaddition manifolds employing
allenamides,27 we anticipated that this cyclopropanation could
proceed stereoselectively by the zinc carbenoid approaching the
bottom p-face of the more favored conformer 1a [Scheme 1]. This
would lead to methylene cyclopropane 2, and while 2 is useful in its
own right,28 an ensuing second cyclopropanation would provide
3a as the major amino-spiro[2.2]pentane isomer with 3b being
derived from cyclopropanation of the minor conformer 1b. We
report here details of these investigations.
or oligo-spirocyclopropane family, represent a unique structural
topology with both rigidity and orthogonality that has found
application in a number of biological contexts.2 In particular,
simple a-spiropentyl acetic acid [Fig. 1] has been shown to mimic
a-(methylenecyclopropyl) acetic acid, a well-known inhibitor
against acyl-CoA dehydrogenase that is critical in the fatty acid
oxidation pathway. In addition, a-(methylenecyclopropyl) acetic
acid itself has also been identified as a toxic metabolite of the natu-
ral amino acid hypoglycine A found in the fruits of Jamaican ackee
trees.3–7 Consequently, it is a key cause of vomiting sickness appear-
ing when ingesting the Jamaican ackee fruit, due to the resulting
deficiency it causes in the acyl-CoA dehydrogenase activity.8,9
Moreover, amino-spiro[2.2]pentanes have received much attention
recently for an array of other purposes ranging from constructing
deoxy-ribonucleotide analogs10 to exploring the chemistry and
biology of spiro[2.2]pentane amino acid derivatives.11,12
Fig. 1 Spiro[2.2]pentanes.
Division of Pharmaceutical Sciences and Department of Chemistry,
Rennebohm Hall, 777 Highland Avenue University of Wisconsin, Madison,
WI 53705-2222, USA. E-mail: rhsung@wisc.edu
† Electronic supplementary information (ESI) available: Experimental
1
procedures, H NMR spectra, characterizations for all new compounds,
and X-ray structural data. CCDC reference numbers 729826–729831. For
ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/b908205k
Scheme 1 Simmons–Smith cyclopropanations of allenamides.
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Table 1 Cyclopropanations of chiral allenamide 7
Results and discussions
1. Cyclopropanations of a-unsubstituted allenamides
The feasibility for Simmons–Smith cyclopropanations of al-
lenamides was quickly established as shown in Scheme 2. By using
5.0 equiv. Et2Zn and 10.0 equiv. ICH2-X, cyclopropanation of
achiral allenamide 4 proceeded in excellent yields to give amido-
spiro[2.2]pentane 629 with no difference between using ICH2-I
and ICH2-Cl respectively in CH2Cl2 and ClCH2CH2Cl [DCE].
We did not observe any mono-cyclopropanation product 5 after
12 h, suggesting that the second cyclopropanation via 5 took place
rapidly in these reactions with Zn(CH2X)2 serving as the highly
reactive cyclopropanating species.30
yield [%] [ratios]b
cyclopropanat.
Entry agent
temp [◦C] solventa
8
9
c
d
1
2
3
4
5
6
7
8
9
10
11
12
13
Zn(CH2CI)2
-20
25
25
85
25
25
25
25
25
25
25
25
25
DCE
–
–
–
Zn(CH2Cl)2
Zn(CH2Cl)2
Zn(CH2Cl)2
Zn(CH2Cl)2
Zn(CH2CI)2
Zn(CH2Cl)2
DCE
67 [1.4:1]
DCEe
DCE
22 [2.8:1] 45 [1.2:1]
–
–
–
50 [1:1]
d
DME
THF
Tol
CH2Cl2
DCE
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
–
d
–
–
–
50 [1:1]
f
Zn(CH2I)2
40 [1.5:1]
d
Zn(CH2I)2–DMEf
CF3CO2ZnCH2Ig
EtZnCH2Ih
10 [1.5:1]
–
–
–
–
d
–
–
–
–
d
d
EtZnCH2I-DMEh
R2AlCH2Ii
d
–
a DCE: 1,2-dichloroethane. DME: 1,2-dimethoxyethane. b NMR yields for
8 and isolated yields for 9. The ratio in brackets denotes a:b with a being
the major isomer as shown in the scheme, and was assigned via NMR.
c Employing 5.0 equiv. Et2Zn and 10.0 equiv. ICH2-Cl. d Recovering 20–
65% of the starting allenamide 7. e conc. = 0.05 M. f Employing 5.0 equiv.
Et2Zn and 10.0 equiv. ICH2-I. For entry 9, 5.0 equiv. of DME was added.
g Employing 5.0 equiv. each of Et2Zn, ICH2-I, and CF3CO2H. h Employing
5.0 equiv. Et2Zn and 5.0 equiv. ICH2-I. For entry 12, 5.0 equiv. of DME
was added. i Employing 5.0 equiv. Me3Al and 5.0 equiv. ICH2-I
Scheme 2 Cyclopropanation of achiral allenamide 4.
We turned our attention to chiral allenamides using specifically
7 [Table 1], and while the cyclopropanation was equally effective in
providing de novo amido-spiro[2.2]pentane 9, the diastereomeric
ratio was not desirable. We explored a range of conditions13a
including different temperatures [entries 1–4] and solvents [entries
5–7], while featuring Zn(CH2Cl)2 as the cyclopropanating species.
In addition, we examined the nature of the cyclopropanating
species such as Zn(CH2I)2 either without [entry 8] or with the
addition of a chelating solvent such as DME [rendering the zinc
cyclopropanating reagent more nucleophilic] [entry 9]. Finally, we
explored Furukawa type reagents [entries 10–12]31,32 as well as
Yamamoto’s AlMe3 activation of ICH2-I [entry 13].33
by only using different cyclopropanating species. It is noteworthy
1
that this effort allowed us to observe by H NMR the mono-
cyclopropanation product 8, although it was not isolated [entries
3 and 9]. This implies that the 2nd cyclopropanation is slower for
chiral allenamides. Stereochemically, both the major and minor
diastereomers of 9 were unambiguously assigned using single-
crystal X-ray structures as shown in Fig. 2. The ability to access
both diastereomers of these structurally very interesting and novel
amido-spiro[2.2]pentanes renders this non-stereoselective aspect
of this reaction an opportunity and less of a limitation.
We did not continue to pursue other cyclopropanating species
such as Molander’s Sm–Hg activation of ICH2-Cl,34 as we
recognized that we were not going to improve the diastereomeric
ratio of amido-spiro[2.2]pentane 9 via bis-cyclopropanation of 7
Fig. 2 X-Ray structures of 9a [left] and 9b [right].
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Subsequently, a number of chiral auxiliaries on the allenamide
were probed in an attempt to improve the diastereoselectivity.
As shown in Scheme 3, amido-spiro[2.2]pentanes such as 10,
11, 14, and 15 could be attained in good yields through bis-
cyclopropanations of their respective allenamides. However, the
diastereomeric ratio remained low, and when employing the
more bulky Sibi’s auxiliary35 or Seebach’s auxiliary,36 the reaction
appeared to be shut down, as only trace amounts of amido-
spiro[2.2]pentanes 12 and 16 could be found. Close’s auxiliary37
gave the best ratio in 17, but with a lower yield. There is essentially
no difference in the level of stereoselectivity between using
auxiliaries containing just the mono-substitution a to the amido-
nitrogen atom [see 10–12] and those with vicinal substitutions on
the oxazolidinone ring [see 14–17].
Scheme 4 Cyclopropanations of E- and Z-enamides.
To rationalize the above stereochemical outcome, we examined
conformations of these enamides through both X-ray structures
[see structures of E-19 and Z-19 in Fig. 3] and PM3 calculations
via Spartan Model.TM Both the X-ray structure [see E-19] and
computation model revealed that E-enamides [R = alkyl or aryl]
assume the more favorable conformation E1 [Scheme 5], which was
what we had speculated earlier in some epoxidation work.38,39 The
other locally minimized conformation is E2 but it is less favored
than E1 by 1.17 kcal mol-1. In both conformers, the olefin is
approaching co-planarity with the oxazolidinone ring, allowing
delocalization of the nitrogen lone pair into the olefin. Being
devoid of actual transition state calculations, we will make an
assumption here that these cyclopropanations proceed through
the major enamide [or allenamide] conformer with the awareness
that the Curtin-Hamett principle could very well be in play here,
Scheme 3 Effect of chiral auxiliaries on stereoselectivity.
2. A comparison with chiral enamides
While the lack of diastereoselectivity was frustrating, it intrigued
us mechanistically. We had previously examined Simmons–Smith
cyclopropanations of chiral enamides and achieved a much greater
success in stereochemical control.17 As shown in Scheme 4, chiral
E-enamides such as 18 and E-19 gave amido-cyclopropanes 20 and
trans-21 with diastereomeric ratios of 95:5 and 83:17, respectively,
while chiral Z-enamides such as 22 and Z-19 led to even higher
diastereomeric ratios of ≥95:5 in each case. These results are in
direct contrast to our current cyclopropanation work.
Scheme 5 A model for the enamide cyclopropanation.
Fig. 3 X-Ray structures of enamides E-19 [left] and Z-19 [right].
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and that we are only attempting to identify a model with some
consistent rationale and predictive power at this juncture.
Based on this assumption, if the cyclopropanation proceeds
through the more favored conformation E1, the necessary
p-facial differentiation in E1 would provide the excellent stereo-
chemical outcome with E2 being a possible source for the minor
diastereomer. On the other hand, in both the X-ray structure [see
Z-19 in Fig. 3] and computation model of Z-enamides, there is
a distinct shift from a coplanar motif in conformation Z1 to
the more favored Z2 [DE = -1.03 to -1.28 kcal mol-1]. This is
likely due to the oxazolidinone ring rotating along the C–N bond
toward the direction such that the Ph substituent could be shifted
away from the R group to alleviate the allylic strain. Despite such
conformational change relative to E-enamides, the bottom p-face
in the more favored conformation Z2 remains sterically more
accessible, thereby providing the same sense of facial selectivity
in the cyclopropanation as for the E-enamide.
difference, if valid, a-substituted allenamides [for R π H] would
then lead to an improved selectivity because 24a is now favored
by 1.05 kcal mol-1 [for R = Me] over 24b due to its the enhanced
allylic strain.
3. Cyclopropanations of a-substituted allenamides
Based on the above conformational model, we prepared a-sub-
stituted achiral allenamides 26–28 [Scheme 7] through a-
alkylation of the respective unsubstituted allenamides.41 Cyclo-
propanations of allenamides 26–28 were not only feasible, but
also led to the observation and isolation of a substantial amount
of mono-cyclopropanation products 29-M through 31-M. In the
case of allenamide 28, we isolated 60% of mono-cyclopropane 31-
M. These results suggest that a-substituted allenamides further
impede the second cyclopropanation compared to unsubstituted
chiral allenamides. The unique structural motif of the amido-
methylene cyclopropane 31-M is displayed in Fig. 4 through its
single-crystal X-ray structure.
Although we have not examined this in detail, the greater
diastereoselectivity attained for Z-enamides relative to those of
E-enamides could be a result of a greater shielding of the top
face by the phenyl ring, and/or a possible chelation of the
oxazolidinone carbonyl oxygen with the zinc reagent in a directed
cyclopropanation manner.
In contrast, while chiral allenamides assume a similar set
of conformations40 as shown in Scheme 6, calculations [PM3
calculations via Spartan ModelTM] suggest that the energetic
difference between conformers 24a and 24b [see DE = -0.21
kcal mol-1 for R = H] appears to be relatively much smaller
than those from enamides. In addition, we also find that the first
cyclopropanation is very facile relative to the cyclopropanation
of enamides. In general, the starting allenamides are consumed
within 1–2 h at 0 ◦C [or rt] based on monitoring by NMR, leading
to 25-Ma and 25-Mb, whereas cyclopropanation of enamides in
most cases required 24–72 h.17 A mixture of mono- and bis-
cyclopropanation products with a ratio of 1:1.5 was usually seen
after 3 h at 0 ◦C, and the long reaction time is associated with the
second cyclopropanation, leading to 25-Ba and 25-Bb.
Scheme 7 Mono- versus bis-cyclopropanation of allenamides.
We proceeded to examine a-substituted chiral allenamides
32–35 as shown in Table 2. In all cases, we isolated both mono-
[36-M through 39-M] and bis-cyclopropanation products [36-B
through 39-B]. A longer reaction time usually resulted in more
of the respective bis-cyclopropanation product. In accord with
our conformational analysis, the diastereomeric ratio was indeed
improved with a dependence on the size of the R groups. The
stereochemistry of 37-B was unambiguously assigned using X-ray
structural analysis [Fig. 4].
To ensure that major isomers of mono- and bis-
cyclopropanation product 37-M and 37-B in fact possess the same
stereochemistry at the carbon bearing the amido group, amido-
methylene cyclopropane 37-M was subjected to the same cyclo-
propanation conditions [Scheme 8]. While the reaction was slow
and incomplete, we found a 43% yield of 37-B [as a single isomer],
thereby confirming that the major isomer of bis-cyclopropanation
products indeed comes from a second cyclopropanation of the
major isomer of the respective mono-cyclopropanation products.
This assessment would then translate the individual ratios of
mono- and bis-cyclopropanation into an excellent overall or
combined diastereoselectivity for the first cyclopropanation [see
numbers in bold] that correlates well overall with increasing size of
Scheme 6 A comparison with the enamide cyclopropanation.
Consequently, again, based on the assumption that these
cyclopropnations also proceed through the major allenamide
conformer, the lack of diastereoselectivity observed in Simmons–
Smith cyclopropanations of allenamides could be due to a
facile cyclopropanation through an almost equal distribution of
unsubstituted allenamide conformers 24a and 24b [for R = H].
While this proposed model is based on ground state energetic
Scheme 8 Assignment of mono-cyclopropane 37-M.
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Table 2 Cyclopropanations of chiral a-substituted allenamides
yield [%] [ratios]a
Mono-cycloprop.
entry
allenamide
R =
time [h]
Bis-cycloprop.
36-B: 26 [3.5:1]
36-B: 36 [3.0:1]
37-B: 18 [≥20:1]
37-B: 22 [≥20:1]
38-B: 20 [≥20:1]
39-B: 23 [≥20:1]
1
2
3
4
5
6
32
32
33
33
34
35
Me
3
16
3
36-M: 38 [3.5:1]
overall dr = 3.5:1b
36-M: 19c [10.0:1]
overall dr = 4.1:1b
37-M: 37d [5.0:1]
overall dr = 7.9:1b
37-M: 30d [6.0:1]
overall dr = 11.1:1b
38-M: 32 [7.0:1]
overall dr =12.0:1b
39-M: 36 [5.0:1]
overall dr = 8.8:1b
Me
n-Bu
n-Bu
16
16
3
Bn
CH2C6H4[o-Ph]
a Isolated yields. Dr ratios are in the bracket with the respective major diastereomer being shown in the scheme and all ratios were assigned using crude
1H NMR. b Overall dr ratios represent the combined dr for the first cyclopropanation. c NMR yield. d See reference 42.
Fig. 4 X-Ray structures of 31-M [left] and 37-B [right].
the R group, and provides a solid support for the conformational
model proposed above.
cyclopropane 5 but saw ent-8 in 12 h under the same reaction
conditions. For a-substituted allenamides, both p-faces of amido-
methylene cyclopropanes such as 29–31 and 36-M through 39-M
are now sterically more encumbered. Consequently, the second
cyclopropanation of 29–31 and 36-M through 39-M should be
slower relative to those of 5 and ent-8, leading to the observation
and/or isolation of methylene cyclopropanes for a-substituted
allenamides.
Lastly, the rate of the second cyclopropanation appears to be
directly correlated with the degree of steric crowding of either
p-face of the methylene cyclopropane intermediate. As shown
in Scheme 9, in the case of unsubstituted allenamides, both
p-faces of the olefin in achiral amido-methylene cyclopropane 5
are open for the second cyclopropanation, whereas chiral amido-
methylene cyclopropane ent-8 is blocked on the bottom p-face with
the top still available. Thus, we did not observe amido-methylene
Conclusion
We have described here Simmons–Smith cyclopropanations of
allenamides in the synthesis of amido-spiro[2.2]pentanes. While
the diastereoselectivity was low when using unsubstituted al-
lenamides, the reaction is overall efficient and general, leading
to an array of amido-spiro[2.2]pentanes. With a-substituted
allenamides, while the diastereoselectivity could be improved
significantly based on a conformational analysis, both mono- and
Scheme 9 Rate comparisons for the second cyclopropanation.
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bis-cyclopropanations were observed in these cases. Consequently,
several structurally intriguing amido-methylene cyclopropanes
could also be prepared. With allenamides being readily accessible,
these efforts have yielded the most straightforward protocol
for constructing chemically and biologically intriguing amido-
spiro[2.2]pentane systems.
(i) F. Brackmann and A. de Meijere, Chem. Rev., 2007, 107, 4493; (j) H.
Pellissier, Tetrahedron, 2008, 64, 7041.
14 For some examples, see: (a) A. B. Charette, E. Jolicoeur and G. A. S.
Bydlinski, Org. Lett., 2001, 3, 3293; (b) M. Lautens and P. H. M.
Delanghe, J. Am. Chem. Soc., 1994, 116, 8526; (c) M. Lautens and
P. H. M. Delanghe, Org. Chem., 1993, 58, 5037; (d) J. A. Russo and
W. A. Price, J. Org. Chem., 1993, 58, 3589; (e) N. S. Zefirov, S. I.
Kozhushkov, T. S. Kuznetsova, K. A. Lukin and I. V. Kazimirchik,
Zh. Org. Khim., 1988, 24, 673; For earlier work, see: (f) E. Ullman and
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H. G. Kuivila, J. Org. Chem., 1966, 31, 772; (h) R. Noyori, H. Takaya,
Y. Nakanisi and H. Nozaki, Can. J. Chem., 1969, 47, 1242; (i) Also see
reference 4.
15 For some examples, see: (a) J. J. Gajewski and L. T. Burka, J. Org.
Chem., 1970, 35, 2190; (b) B. M. Trost and M. J. Bogdanowicz, J. Am.
Chem. Soc., 1973, 95, 5307; (c) N. S. Zefirov, S. I. Kozhushkov, B. I.
Ugrak, K. A. Lukin, O. V. Kokoreva, D. S. Yufit, Y. T. Struchkov, S.
Zoellner, R. Boese and A. Demeijere, J. Org. Chem., 1992, 57, 701;
(d) M. Weber and A. de Meijere, Chem. Ber., 1986, 118, 2450; (e) I. V.
Akhachinskauya, N. A. Donskaya, I. V. Kalykina, Y. F. Oprunenko
and Y. S. Shabarov, Zh. Org. Khim., 1989, 25, 1645; (f) C. Cheng, T.
Shimo, K. Somekawa and M. Kawaminami, Tetrahedron Lett, 1997, 52,
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Sciences, 2006, 5, 1000; (h) Also see reference 4.
Acknowledgements
The authors thank NIH-NIGMS [GM066055] for funding. We
thank Mr Benjiman E. Kucera and Dr Vic Young of University of
Minnesota for providing X-ray structural analysis.
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3336 | Org. Biomol. Chem., 2009, 7, 3331–3337
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The Royal Society of Chemistry 2009
©

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[I > 2s(I)], R1 = 0.0329, wR2 = 0.0756, R indices (all data) R1 = 0.0416,
wR2 = 0.0815. Crystallographic data for E-19: C17H15NO2, M = 265.30,
orthorhombic, P212121, a = 6.0167(5), b = 10.2379(9), c = 22.355(2)
◦
3
˚
˚
A, a = 90, b = 90, g = 90 , V = 1377.0(2) A , T = 173(2) K, Z = 4,
m = 0.084 mm-1, 1790(Rint= 0.0439), final R indices [I > 2s(I)], R1 =
0.0329, wR2 = 0.0761, R indices (all data) R1 = 0.0460, wR2 = 0.0803.
Crystallographic data for Z-19: C17H15NO2, M = 265.30, monoclinic,
˚
C2, a = 30.294(8), b = 6.4077(17), c = 7.0525(19) A, a = 90, b =
◦
3
´
˚
904; (g) A. Gonza´lez-Go´mez, L. An˜orbe, A. Poblador, G. Dom´ınguez
100.238(4), g = 90 , V = 1347.2(6) A , T = 173(2) K, Z = 4, m =
and J. Pe´rez-Castells, Eur. J. Org. Chem., 2008, 1370; (h) A. Navarro-
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0.086 mm-1, 1492(Rint = 0.0503), final R indices [I > 2s(I)], R1
=
0.0394, wR2 = 0.0868, R indices (all data) R1 = 0.0553, wR2 = 0.0922.
Crystallographic data for 31M: C20H19NO2, M = 305.36, monoclinic,
˚
P21/n, a = 10.3033(13), b = 10.2448(13), c = 15.332(19) A, a = 90,
◦
3
˚
b = 95.088(2), g = 90 , V = 1612.0(4) A , T = 173(2) K, Z = 4,
m = 0.081 mm-1, 3678(Rint = 0.0269), final R indices [I > 2s(I)], R1 =
0.0415, wR2 = 0.1043, R indices (all data) R1 = 0.0584, wR2 = 0.1178.
Crystallographic data for 37B: C18H23NO2, M = 285.37, monoclinic,
˚
P21/n, a = 6.2307(11◦), b = 16.094(3), c = 8.0544(15) A, a = 90,
3
˚
b = 96.906(2), g = 90 , V = 801.8(3) A , T = 173(2) K, Z = 2, m =
0.076 mm-1, 1704(Rint= 0.0328), final R indices [I > 2s(I)], R1 = 0.0342,
wR2 = 0.0811, R indices (all data) R1 = 0.0425, wR2 = 0.0861.
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42 An unexpected oxidative product i [see below] was found in the reaction
mixture. Compound i was also seen during the purification of chiral
allenamide 33, but we are not certain of its origin at this point.
29 See ESI.† Crystallographic data for 9a: C14H15NO2, M = 229.27,
˚
triclinic, P1, a = 6.2295(4), b = 11.8164(7), c ◦= 12.8744(8) A, a =
3
˚
84.5470(10), b = 86.5820(10), g = 76.4120(10) , V = 916.30(10) A ,
T = 173(2) K, Z = 3, m = 0.083 mm-1, 3730(Rint= 0.0242), final R
indices [I > 2s(I)], R1 = 0.0320, wR2 = 0.0732, R indices (all data)
R1 = 0.0424, wR2 = 0.0793. Crystallographic data for 9b: C14H15NO2,
M = 229.27, orthorhombic, P212121, a = ◦6.4331(18), b = 11.657(3),
3
˚
˚
c = 15.860(4) A, a = 90, b = 90, g = 90 , V = 1189.4(6) A , T =
173(2) K, Z = 4, m = 0.086 mm-1, 1265(Rint= 0.0431), final R indices
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The Royal Society of Chemistry 2009
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