Hydroboration of 1,1′-bi(cyclopent-1-ene) and 3,3′-biindene: Experimental and theoretical study

Article abstract of DOI:10.1135/cccc20061611

Hydroboration of bi(cyclopent-1-ene) (1) or 3,3′-biindene (2) with borane, thexylborane or (-)-isopinocampheylborane afforded, regardless of reaction conditions, meso-isomers of polycyclic 1,4-diols 3a, 4a as the main products. No reaction was observed with 9-BBN. The structure of the major product 4a, as well as of the minor racemic product 4b was assigned based on ¹H NMR spectra of the corresponding Mosher's diesters 5a-5c. Finally, the stereochemistry of the product 4a was confirmed by a single-crystal X-ray analysis of the corresponding dimesylate 6. To elucidate preferential formation of the weso-isomers, complexes of monohydroborated intermediate with borane were studied theoretically by DFT methods.

Full text of DOI:10.1135/cccc20061611

Hydroboration of 1,1′-Bi(cyclopent-1-ene) and 3,3′-Biindene
1611
HYDROBORATION OF 1,1′-BI(CYCLOPENT-1-ENE) AND
3
,3′-BIINDENE: EXPERIMENTAL AND THEORETICAL STUDY
1
,
2
3
Jaroslav KVÍČALA *, Ondřej BASZCZYŇSKI , Alena KRUPKOVÁ and
Denisa STRÁNSKÁ4
Department of Organic Chemistry, Institute of Chemical Technology, Prague, Technická 5,
1
2
1
66 28 Prague 6, Czech Republic; e-mail: jaroslav.kvicala@vscht.cz, baszczyo@vscht.cz,
3
4
krupkova@icpf.cas.cz, horcicod@vscht.cz
Received Septem ber 8, 2006
Accepted October 24, 2006
Hydroboration of bi(cyclopen t-1-en e) (1) or 3,3′-biin den e (2) with boran e, th exylboran e or
–)-isopin ocam ph eylboran e afforded, regardless of reaction con dition s, meso-isom ers of
(
polycyclic 1,4-diols 3a, 4a as th e m ain products. No reaction was observed with 9-BBN. Th e
structure of th e m ajor product 4a, as well as of th e m in or racem ic product 4b was assign ed
1
based on H NMR spectra of th e correspon din g Mosh er’s diesters 5a –5c. Fin ally, th e
stereoch em istry of th e product 4a was con firm ed by a sin gle-crystal X-ray an alysis of th e
correspon din g dim esylate 6. To elucidate preferen tial form ation of th e meso-isom ers, com -
plexes of m on oh ydroborated in term ediate with boran e were studied th eoretically by DFT
m eth ods.
Keywords: Dien es; Asym m etric h ydroboration ; Boran es; Ch iral diols; Mosh er’s esters; Absolute
con figuration ; DFT calculation s; X-ray diffraction .
Ch iral diols ran k am on g th e m ain groups of com poun ds form in g a ch iral
pool in organ ic syn th esis. Alth ough th ey can be used directly as ligan ds in
1
m an y catalytic reaction s , th eir key application area con sists in tran sform a-
tion s to oth er classes of ch iral substan ces. Am on g th em , ch iral diph os-
ph in es are em ployed exten sively as ch iral ligan ds in en an tioselective
catalytic reaction s an d attract th us th e atten tion of both academ ic an d in -
2
,3
dustrial ch em ists . Th e aim s to ach ieve still h igh er yields an d en an tio-
selectivities of catalytic processes result in con tin uous search for n ew
ligan ds.
4
Quite recen tly, bi(cyclopen tan e) based ligan ds were syn th esized an d em -
4
–9
ployed in various catalytic reaction s, e.g. asym m etric h ydrogen ation
,
1
0
11
cyclocarbon ylation , or cycloisom erization . Th e key precursor, ch iral
,1′-bi(cyclopen tan e)-2,2′-diol (3) was syn th esized by en an tioselective
4
1
h ydroboration of bi(cyclopen t-1-en e) (1) with isopin ocam ph eylboran e
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626
©
2006 Institute of Organic Chemistry and Biochemistry
doi:10.1135/cccc20061611

1
612
Kvíčala, Baszczyňski, Krupková, Stránská:
1
2
(
pin an -3-ylboran e) . Un fortun ately, n eith er experim en tal details n or yields
1
3
were publish ed. In th e correspon din g paten t , wh ich in cludes th e detailed
description of th e h ydroboration experim en t, on ly 18% yield of ch iral diol
3
b is claim ed, th e meso-diol 3a bein g th e m ain reaction product. Th e re-
cen tly publish ed im proved procedure in cluded th e preparation of rac-diol
b followed by en zym atic resolution 14. Again , n o experim en tal details of
3
th e preparation of rac-diol 3b were in cluded. Th e origin al ach iral version of
h ydroboration of dien e 1 with th e boran e–THF com plex was probably em -
1
5
ployed , wh ich afforded th e target diol 3b in a 15% yield togeth er with th e
m ajor product, meso-diol 3a.
In con trast to th e h ydroboration of dien e 1, en an tioselective h ydro-
boration of 3,3′-biin den e (2) with isopin ocam ph eylboran e was reported to
1
6
give th e correspon din g ch iral 1,1′-biin dan e-2,2′-diol (4) in a good yield
.
1
6
Ch iral diol 4 was em ployed in en an tioselective alkylation of aldeh ydes
1
7
an d en an tioselective reduction of keton es .
In th e course of our search for n ovel ch iral boran es an d silan es, we en vis-
aged ch iral diols 3 an d 4 as useful precursors for th eir syn th eses. Due to th e
absen ce of full experim en tal details in th e case of dien e 1 an d an un kn own
com position of th e crude reaction m ixture in th e case of dien e 2 we de-
cided to start a sh ort experim en tal an d th eoretical study of h ydroboration
of th is class of dien es.
EXPERIMENTAL
Tem perature data were un corrected. NMR spectra were recorded with a Varian MercuryPlus
1
13
spectrom eter, H NMR spectra at 299.97 MHz an d C NMR spectra at 75.43 MHz usin g re-
1
9
sidual deuterated solven t sign als as th e in tern al stan dards, F NMR spectra at 282.23 MHz
usin g CCl F as th e in tern al stan dard. Ch em ical sh ifts are given in ppm , couplin g con stan ts
3
in Hz. In som e cases, gCOSY an d gHSQC experim en ts were accom plish ed to allow full as-
sign m en t of sign als. FTIR spectra were recorded with an FT-IR Nicolet 740 in strum en t in
CHCl . Elem en tal an alyses were perform ed with an Elem en tar Vario EI III in strum en t. Mass
3
spectra were m easured with an Autospec Ultim a (Microm ass) in strum en t.
All reaction s were perform ed in dry in ert atm osph ere in oven -dried apparatuses.
Cyclopen tan on e (99%), in den e (tech n ical grade, 90%), Cu(II) ch loride (97%), butyllith ium
(
2.5 M solution in h exan es), boran e–THF com plex (1 M in THF), 2,3-dim eth ylbut-2-en e (1
in THF), bis[(–)-isopin ocam ph eylboran e]–TMEDA com plex ((R)-Alpin e–Boram in eTM), 9-BBN
9-borabicyclo[3.3.1]n on an e; 0.5 in THF), m esyl ch loride an d (+)-(S)-3,3,3-trifluoro-
-m eth oxy-2-ph en ylpropion yl ch loride (7; ch loride of Mosh er’s acid, 99%, 99.5% ee) were
M
(
2
M
purch ased from Aldrich . Dieth yl eth er an d THF were dried over sodium ben zoph en on e ketyl
an d distilled prior to use. Cupric ch loride was dried at 80 °C in vacuo for 12 h , followed by
coolin g in dry in ert atm osph ere.
1
,1′-Bicyclopen tan e-1,1′-diol was prepared by reductive couplin g of cyclopen tan on e with
1
8
alum in um , catalyzed with m ercuric ch loride accordin g to ref. in a 66% yield. Its deh ydra-
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

Hydroboration of 1,1′-Bi(cyclopent-1-ene) and 3,3′-Biindene
1613
tion with acetic an h ydride accordin g to ref.19 afforded bi(cyclopen t-1-en e) (1) in a 70%
yield. 1,1′-Biin den e was prepared by oxidative couplin g with butyllith ium an d Cu(II) ch lo-
2
0
ride in an 85% yield as a 60:40 m ixture of meso- an d rac-diastereoisom ers . Th exylboran e
2
1
[
(1,1,2-trim eth ylpropyl)boran e] was prepared prior to use by m ixin g equivalen t am oun ts
of BH –THF com plex solution an d 2,3-dim eth ylbut-2-en e solution at 0 °C. (–)-Isopin o-
3
cam ph eylboran e was prepared prior to use by m ixin g bis[(–)-isopin ocam ph eylboran e]–TMEDA
com plex, dissolved in THF, with boron trifluoride eth erate, followed by rem oval of in soluble
1
2
salts by filtration un der in ert gas
.
3
,3′-Biin den e (2)
A 250-m l flask equipped with a m agn etic stirbar was ch arged with 1,1′-biin den e (7.00 g,
3
0.4 m m ol, 60:40 m ixture of meso- an d rac-diastereoisom ers) an d dich lorom eth an e (30 m l).
To th e stirred m ixture was dropwise added trieth ylam in e (12.3 g, 16.9 m l, 121 m m ol) at
room tem perature an d th e m ixture was stirred for 4 h . Th e solven t an d trieth ylam in e were
rem oved on vacuum rotary evaporator. Th e target dien e 2 (6.4 g, 91%, ligh t yellow crystals,
2
0
m .p. 126–128 °C, ref. 131 °C) was obtain ed by recrystallization from m eth an ol. Th e product
2
0
gave NMR spectra iden tical with th e publish ed data
.
Hydroboration of Dien es 1, 2. Gen eral Procedure
A h ydroboration reagen t was dissolved in THF, cooled to th e desired tem perature an d dien e
or 2, dissolved in THF, was added dropwise wh ile stirrin g. Th e stirrin g was con tin ued at
th e sam e tem peratu re. Th e m ixtu re was q u en ch ed by a dropwise addition of m eth an ol
1
(
2 m l/ m m ol of dien e) an d allowed to warm to room tem peratu re. Aq u eou s H O (30%,
2 2
4
m l/m m ol of dien e) an d 3 M NaOH solution (4 m l/m m ol of dien e) were added dropwise
wh ile stirred an d th e m ixture was h eated to 55 °C for 1 h . After coolin g, th e organ ic layer
was separated, th e aqueous layer was extracted 3 tim es with eth yl acetate (dien e 1) or di-
eth yl eth er (dien e 2). Com bin ed organ ic layers were evaporated on vacuum rotary evapora-
tor, redissolved in th e above solven t an d extracted with water. Th e separated organ ic layer
was dried with an h ydrous MgSO . Fin al evaporation afforded crude product m ixture, wh ich
4
was purified by colum n ch rom atograph y (silica, eluen t dich lorom eth an e/m eth an ol 12:1 for
dien e 1, dich lorom eth an e/m eth an ol 24:1 for dien e 2). As a rule, product of th e oxidation of
th e h ydroboration reagen t (2,3-dim eth ylbutan -2-ol or pin an -3-ol) was eluted first, followed
by m in or rac-diastereoisom er (if obtain ed) 3b or 4b. Th e last com poun d eluted was m ajor
meso-diastereoisom er 3a or 4a.
Hydroboration of Bi(cyclopen t-1-en e) (1) with Boran e–THF Com plex15 (Run 1)
7
.13 g (53.1 m m ol) of dien e 1 an d 127.5 m l (127.5 m m ol) of BH ·THF solution afforded
3
after 20-h reaction at room tem perature an d isolation meso-diastereoisom er
*
*
*
*
(
1R ,1′S ,2S ,2′R )-1,1′-bi(cyclopen tan e)-2,2′-diol (3a; 3.71 g, 41.0%, wh ite crystals, m .p.
1
5
*
*
*
1
2
1
(
(
42–145 °C, ref. 145 °C) an d rac-diastereoisom er (1R*,1′R ,2S ,2′S )-1,1′-bi(cyclopen tan e)-
,2′-diol (3b; 0.79 g, 8.7%, wh ite crystals, m .p. 90–105 °C, ref.15 109 °C). Diol 3a: H NMR
.20–1.40 m , 2 H (CHH); 1.48–1.94 m , 12 H (CH , CH); 4.00 dt, 2 H, JHH = 6.9 (d), 4.8 (t)
CHOH); 4.96 bs,
1
15
:
3
2
1
3
2
H
(OH).
C NMR: 22.4 (CH CH CH ); 28.8 (CHCH ); 35.1
2 2 2 2
1
15,21
CH(OH)CH ); 50.9 (CH); 75.7 (CHOH). Diol 3b: H NMR
.37–1.80 m , 10 H (CH , CH); 1.90–2.02 m (CHH); 3.79 q, 3J
2 HH
: 1.07–1.21 m , 2 H (CHH);
= 8.0 (CHOH); 4.96 bs, 2 H
2
1
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

1
614
Kvíčala, Baszczyňski, Krupková, Stránská:
(
(
OH). HSQC 1.13, 2 H (CHH); 1.41, 2 H (CH); 1.50, 2 H (CHH); 1.57, 2 H (CHH); 1.68, 2 H
1
3
21
CHH); 1.75, 2 H (CHH); 1.97, 2 H (CHH); 3.79 (CHOH). C NMR : 20.5 (CH CH CH );
2 2 2
2
9.3 (CHCH ); 33.6 (CH(OH)CH ); 52.2 (CH); 78.6 (CHOH).
2 2
Hydroboration of Bi(cyclopen t-1-en e) (1) with Th exylboran e (Run 2)
1
2
.10 g (8.20 m m ol) of dien e 1, 25 m l (25.0 m m ol) of BH ·THF an d 25 m l (25.0 m m ol) of
3
,3-dim eth ylbut-2-en e afforded, after 14-h reaction at 0 °C an d isolation , 558 m g (40.0%) of
1
m ixture of meso-diastereoisom er 3a an d rac-diastereoisom er 3b in a 93:7 ratio ( H NMR).
Hydroboration of Bi(cyclopen t-1-en e) (1) with (–)-Isopin ocam ph eylboran e (Run 4)
4
48 m g (3.34 m m ol) of dien e 1, 2.50 g (6.00 m m ol) of bis[(–)-isopin ocam ph eylboran e]–
TMEDA com plex an d 1.70 g (12.0 m m ol) of BF ·Et O afforded, after 24-h reaction at –25 °C
3
2
an d isolation , 337 m g (59.3%) of meso-diastereoisom er 3a. No rac-diastereoisom er 3b was
isolated.
Hydroboration of Bi(cyclopen t-1-en e) (1) with Equivalen t of (–)-Isopin ocam ph eylboran e
(
Run 8)
2
68 m g (2.00 m m ol) of dien e 1, 416 m g (1.00 m m ol) of bis[(–)-isopin ocam ph eyl-
boran e]–TMEDA com plex an d 284 m g (2.00 m m ol) of BF ·Et O afforded, after 18-h reaction
3
2
at room tem perature an d isolation , 112 m g (32.9%) of th e m ixture of meso-diastereoisom er
1
3
a an d rac-diastereoisom er 3b in a 74:26 ratio ( H NMR).
Hydroboration of Bi(cyclopen t-1-en e) (1) with 9-BBN (Run 9)
After 20-h reaction of dien e 1 (300 m g, 2.24 m m ol) with 9-BBN (11.0 m l, 5.5 m m ol) at
room tem perature, on ly startin g com poun d 1 was isolated.
Hydroboration of 3,3′-Biin den e (2) with Boran e–THF Com plex (Run 10)
1
.15 g (5.00 m m ol) of dien e 2 an d 12.0 m l (12.0 m m ol) of BH ·THF afforded after 20-h reac-
3
tion at room tem perature an d isolation 1.221 g (91.8%) of a m ixture of meso-diastereoisom er
*
*
*
*
*
*
*
*
(
1R ,1′S ,2R ,2′S )-1,1′-biindane-2,2′-diol (4a) and rac-diastereoisomer (1R ,1′R ,2R ,2′R )-1,1′-biindane-
2
3
,2′-diol (4b) in a 73:27 ratio. By repeated colum n ch rom atograph y, meso-diol 4a (500 m g,
1
6
7.6%, RF 0.24 in CH Cl /MeOH 16:1, ligh t yellow crystals, m .p. 115–116 °C, ref. 116 °C)
2
2
an d rac-diol 4b (199 m g, 15.0%, R 0.28 in CH Cl /MeOH 16:1, ligh t yellow crystals, m .p.
F
2
2
16
6
4–66 °C). Diol 4a : 1H NMR 16 (in ref. , th e spectrum was erron eously assign ed to
2
3
rac-diastereoisom er 4b): 1.92 bs, 2 H (OH); 2.83 dd, 2 H, JHH = 16.1, JHH = 5.3 (CHH); 3.19
dd, 2 H, JHH = 16.1, JHH = 7.0 (CHH); 3.61 d, 2 H, JHH = 4.4 (CH); 4.54 dt, 2 H, JHH = 7.0
d), JHH = 5.3 (t) (CHOH); 6.88 d, 2 H, JHH = 7.7 (CArH); 7.07–7.28 m , 6 H (CArH). 13C NMR:
2
3
3
3
3
3
(
4
1
4
2
1.3 (CH ); 54.9 (CH); 75.9 (CHOH); 124.5 (CArH); 124.9 (CArH); 126.8 (CArH); 127.2 (CArH);
2
40.9 (CAr); 142.1 (CAr). Diol 4b: H NMR: 2.35 bs, 2 H (OH); 2.88 dd, 2 H, 2J = 16.5, 3J
1
=
HH
HH
2
= 16.5, 3JHH = 6.6 (CHH); 3.60 d, 2 H, JHH = 2.8 (CH); 4.32 ddd,
3
.4 (CHH); 3.29 dd, 2 H,
J
HH
3
3
3
3
H, JHH = 6.6, JHH = 4.4, JHH = 2.8 (CHOH); 7.12 d, 2 H, JHH = 7.2 (CArH); 7.20–7.34 m , 6 H
1
3
(
(
CArH). C NMR: 41.0 (CH ); 55.5 (CH); 75.7 (CHOH); 125.0 (CArH); 125.0 (CArH); 126.5
CArH); 127.2 (CArH); 140.6 (CAr); 142.0 (CAr). MS (EI), m/z (%): 266 [M, 3], 248 [(M – H O),
2
2
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

Hydroboration of 1,1′-Bi(cyclopent-1-ene) and 3,3′-Biindene
1615
7
8], 230 [(M – 2 H O), 27], 134 [(M/2 + H), 89], 116 [(M/2 + H – H O), 100]. For C18H18O2
2
2
(
266.3) calculated: 81.17% C, 6.81% H; foun d: 80.54% C, 7.05% H.
Hydroboration of 3,3′-Biin den e (2) with Th exylboran e (Run 11)
2
2
2
.31 g (10.0 m m ol) of dien e 2, 30 m l (30.0 m m ol) of BH ·THF an d 30 m l (30.0 m m ol) of
,3-dim eth ylbut-2-en e afforded, after 20-h reaction at room tem perature an d isolation ,
3
.96 g of crude product con tain in g 2,3-dim eth ylbutan -2-ol, meso-diastereoisom er 4a an d
1
rac-diastereoisom er 4b (82:18 ratio, H NMR). By secon d colum n ch rom atograph y an d
recrystallization , 1.36 g (50.9%) of pure crystallin e diol 4a was obtain ed.
Hydroboration of 3,3′-Biin den e (2) with (–)-Isopin ocam ph eylboran e (Run 12)
1
.15 g (5.00 m m ol) of dien e 2, 3.12 g (7.5 m m ol) of bis[(–)-isopin ocam ph eylboran e]–TMEDA
com plex an d 1.90 m l (2.13 g, 15.0 m m ol) of BF ·Et O afforded, after 24-h reaction at room
3
2
1
tem perature an d isolation , 3.107
g of crude product con tain in g ( H NMR) 68% of
2
3
pin an -3-ol an d 32% of diols 4 (estim ated yield 74%, 4a:4b = 85:15). Separation of diols 4
from pin an -3-ol was tedious, required repeated colum n ch rom atograph y an d furn ish ed fi-
n ally 242 m g (18.2%) of meso-diol 4a an d 73 m g (5.5%) of rac-diol 4b. Diol 4b sh owed n o
optical rotation an d also its tran sform ation to Mosh er’s diesters 5 con firm ed its racem ic
structure (see below).
Hydroboration of 3,3′-Biin den e (2) with 9-BBN (Run 13)
After 20-h reaction of dien e 2 (200 m g, 0.87 m m ol) with 9-BBN (4.5 m l, 2.3 m m ol) at room
tem perature, on ly startin g com poun d 2 was isolated.
Preparation of Esters of Mosh er’s Acid 5 from Diols 4. Gen eral Procedure24
To
+)-(S)-3,3,3-trifluoro-2-m eth oxy-2-ph en ylpropan oyl ch loride (7; 37 µl, 51 m g, 200 µm ol)
was syrin ged at room tem perature. Th e m ixture was cooled to 0 °C an d pyridin e (8 µl, 8 m g,
a stirred solution of diol 4 (13 m g, 50 µm ol) in dry dich lorom eth an e (1 m l),
(
1
5
00 µm ol) was added. Th e m ixture was allowed to warm to room tem perature an d stirred for
h . To th e crude m ixture, dieth yl eth er (15 m l) an d brin e (15 m l) were added, organ ic layer
was separated an d wash ed successively with h ydroch loric acid (5%, 15 m l), brin e (15 m l),
saturated solution of NaHCO3 (15 m l) an d brin e (15 m l). Dryin g with an h ydrous MgSO4 an d
rem oval of solven ts on vacuum rotary evaporator afforded th e crude reaction m ixture,
1
wh ich was an alyzed by H NMR an d separated to in dividual diesters 5 an d m on oesters 8 by
colum n ch rom atograph y (silica, eluen t CHCl /MeOH 99:1).
3
*
*
*
*
Reaction of Acyl Ch loride 7 with meso-(1R ,1′S ,2R ,2′S )-1,1′-Biin dan e-2,2′-diol (4a)
Reaction of diol 4a with acyl ch loride 7 afforded 50 m g of crude reaction m ixture con tain -
1
in g ( H NMR) 20% (1R,1′S,2R,2′S)-1,1′-biin dan e-2,2′-diyl bis[(R)-3,3,3-trifluoro-2-m eth oxy-
2
2
-ph en ylpropan oate] (5a), 25% (1R,1′S,2R,2′S)-2′-h ydroxy-1,1′-biin dan -2-yl (R)-3,3,3-trifluoro-
-m eth oxy-2-ph en ylpropan oate (8a ), 43% (1S,1′R,2S,2′R)-2′-h ydroxy-1,1′-biin dan -2-yl
(
R)-3,3,3-trifluoro-2-m eth oxy-2-ph en ylpropan oate (8b) an d 12% of startin g diol 4a togeth er
with som e un reacted Mosh er’s acid. Ch rom atograph ic separation afforded 5 m g (15%) of
1
diester 5a an d 6 m g (25%) of a 37:63 m ixture of m on oesters 8a, 8b. Diester 5a: H NMR:
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

1
616
Kvíčala, Baszczyňski, Krupková, Stránská:
2
.81 dd, 1 H, 2JHH = 17.6, 3JHH = 3.0 (cis-3-CHH); 2.94 dd, 1 H, 2J
= 17.6, 3J
= 3.3
HH
HH
cis-3′-CHH); 3.19 dd, 1 H, 2J
= 17.6, JHH = 7.1 (trans-3-CHH); 3.26 dd, 1 H, 2J
3
= 17.6,
HH
(
HH
3
= 7.1 (trans-3′-CHH); 3.50 q, 3 H, 5J = 1.1 (OCH ); 3.52 q, 3 H, JHF = 1.1 (OCH );
5
J
HH
HF 3 3
.81 t, 1 H, 3JHH = 3.0 (1′-CH); 3.84 t, 1 H, JHH = 3.0 (1-CH); 5.40 dt, 1 H, JHH = 7.1 (d),
3
3
3
3
3
3
JHH = 3.0 (t) (2-CHO-); 5.46 dt, 1 H, JHH = 6.9 (d), JHH = 3.3 (t) (2′-CHO-); 6.66 d, 2 H,
3J
= 7.2 (CArH); 7.08 t, 2 H, JHH = 7.2 (CArH); 7.13–7.26 m , 4 H (CArH); 7.36–7.43 m , 6 H
3
HH
1
3
(
CPh H); 7.48–7.51 m , 4 H (CPh H). C NMR: 38.5 (CH ); 38.7 (CH ); 54.2 (CH); 54.3 (CH);
2 2
1
5
1
5.4, 2 C (OCH ); 80.1 (CHO-); 80.4 (CHO-); 123.2 q, 2 C (CF ), JCF = 288; 124.3 (CArH);
3 3
24.3 (CArH); 124.7 (CArH); 124.8 (CArH); 127.1 (CArH); 127.2, 5 C (CArH + 4 CPh H); 127.9, 2 C
(
(
CPh H); 128.5, 4 C (CPh H); 129.6 (CArH); 129.7 (CArH); 132.0, 2 C (CPh ); 140.3 (CAr); 140.3
CAr); 140.4, 2 C (CAr); 166.5, 2 C (C=O); th e quatern ary C of propan oyl was n ot foun d due
2
1
9
1
to low in ten sity an d splittin g by CF group. F NMR: –71.9, s. Mon oester 8a: H NMR:
2
3
.84 dd, 1 H, 2JHH = 17.2, JHH = 4.3 (cis-3′-CHH); 2.85 dd, 1 H, JHH = 17.2, 3J
3
2
= 4.3
HH
cis-3-CHH); 3.29 dd, 1 H, 2J
= 17.2, JHH = 6.9 (trans-3′-CHH); 3.25 dd, 1 H, 2J
JHH = 7.1 (trans-3-CHH); 3.51 q, 3 H, 5J = 1.1 (OCH ); 3.63 dd, 1 H, JHH = 4.7, JHH = 4.3
1′-CH); 3.91 t, 1 H, JHH = 4.3 (1-CH); 4.47 dt, 1 H, JHH = 6.9 (d), JHH = 5.4 (t) (2′-CHOH);
.57 dt, 1 H, 3JHH = 7.1 (d), JHH = 3.6 (t) (2-CHO-); 6.67 d, 1 H, JHH = 7.2 (CArH); 6.89 d, 2 H,
3
= 17.2,
HH
(
3
HH
3
3
HF
3
3
3
3
(
3
3
5
3
JHH = 7.2 (CArH); 7.01–7.24 m , 6 H (CArH); 7.36–7.43 m , 3 H (CPh H); 7.48–7.51 m , 2 H
1
3
(
1
C
9
H). C NMR could n ot be assign ed from th e m ixture due to h igh com plexity of sign als.
Ph
1
2
3
F NMR: –71.8, s. Mon oester 8b: H NMR: 2.80 dd, 1 H, JHH = 16.4, JHH = 5.1 (cis-3′-CHH);
.97 dd, 1 H, JHH = 16.4,
trans-3′-CHH); 3.34 dd, 1 H,
OCH ); 3.60 dd, 1 H, JHH = 5.1, JHH = 4.3 (1′-CH); 3.84 t, 1 H, JHH = 4.3 (1-CH); 4.32 dt, 1 H,
2
3
= 4.3 (cis-3-CHH); 3.11 dd, 1 H, 2J
3
2
J
= 16.4, JHH = 6.9
HH
HH
2
3
5
(
(
J
= 16.4, JHH = 7.1 (trans-3-CHH); 3.52 q, 3 H, JHF = 1.4
HH
3
3
3
3
3
3
3
3
JHH = 6.9 (d), JHH = 5.6 (t) (2′-CHOH); 5.53 dt, 1 H, JHH = 7.1 (d), JHH = 4.4 (t) (2-CHO-);
.59 d, 1 H, 3J
= 7.2 (CArH); 6.89 d, 2 H, JHH = 7.2 (CArH); 7.01–7.24 m , 6 H (CArH);
HH
3
6
7
.36–7.43 m , 3 H (CPh -H); 7.48–7.51 m , 2 H (C -H). 13C NMR could n ot be assign ed from
Ph
1
9
th e m ixture due to h igh com plexity of sign als. F NMR: –72.0, s.
*
*
*
*
Reaction of Acyl Ch loride 7 with rac-(1R ,1′R ,2R ,2′R )-1,1′-Biin dan e-2,2′-diol (4b)
Reaction of diol 4b with acyl ch loride 7 afforded 47 m g of crude reaction m ixture con tain -
1
in g ( H NMR) 15% (1R,1′R,2R,2′R)-1,1′-biin dan e-2,2′-diyl bis[(R)-3,3,3-trifluoro-2-m eth oxy-
2
2
-ph en ylpropan oate] (5b), 16% (1S,1′S,2S,2′S)-1,1′-biin dan e-2,2′-diyl bis[(R)-3,3,3-trifluoro-
-m eth oxy-2-ph en ylpropan oate] (5c), 19% (1R,1′R,2R,2′R)-2′-h ydroxy-1,1′-biin dan -2-yl
(
1
R)-3,3,3-trifluoro-2-m eth oxy-2-ph en ylpropan oate (8c), 38% (1S,1′S,2S,2′S)-2′-h ydroxy-
,1′-biin dan -2-yl (R)-3,3,3-trifluoro-2-m eth oxy-2-ph en ylpropan oate (8d ) an d 12% startin g
diol 4b togeth er with som e un reacted Mosh er’s acid. Ch rom atograph ic separation afforded
1
3
m g (3%) of diester 5b, 1 m g (3%) of a 1:1 m ixture of diesters 5b, 5c, 4 m g (12%) of a
9:61 m ixture of diesters 5b, 5c an d 9 m g (38%) of a 28:72 m ixture of m on oesters 8c, 8d .
1
2
3
5
Diester 5b: H NMR: 2.97 dd, 2 H, JHH = 17.7, JHH = 2.1 (cis-3,3′-CHH); 3.32 q, 6 H, JHF
=
.1 (OCH ); 3.41 s, 2 H (1,1′-CH); 3.60 dd, 2 H, 2J
= 17.7, JHH = 6.0 (trans-3,3′-CHH); 5.90
HH
= 7.1 (CArH); 7.04–7.12 m , 2 H (CArH);
HH
.19–7.29 m , 4 H (CArH); 7.32–7.42 m , 10 H (C H). 13C NMR: 37.7 (CH ); 53.2 (CH); 55.3
3
1
3
d, 2 H, JHH = 6.0 (2,2′-CHO-); 6.70 d, 2 H, 3J
3
7
P
h
2
1
(
(
(
OCH ); 81.5 (CHO-); 123.2 q, 2 C (CF ), JCF = 288; 125.0 (CArH); 126.3 (CArH); 127.2
3 3
CArH); 127.9 (CArH + CPh H); 128.3 (CPh H); 129.5 (CPh H); 132.0 (CPh ); 140.2 (CAr); 140.4
CAr); 166.6, 2 C (C=O); quatern ary C atom of propan oyl was n ot foun d due to low in ten -
2
1
9
1
2
sity an d splittin g by CF3 group. F NMR: –72.2, s. Diester 5c: H NMR: 3.03 dd, 2 H, JHH
=
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

Hydroboration of 1,1′-Bi(cyclopent-1-ene) and 3,3′-Biindene
1617
1
2
7.8, 3J
= 1.9 (cis-3,3′-CHH); 3.35 q, 6 H, 5J = 1.1 (OCH ); 3.49 s, 2 H (1,1′-CH); 3.59 dd,
HH HF 3
H, 2JHH = 17.8, JHH = 6.2 (trans-3,3′-CHH); 5.62 d, 2 H, JHH = 6.2 (2,2′-CHO-); 6.78 d, 2 H,
3
3
3
JHH = 7.7 (CArH); 7.04–7.12 m , 2 H (CArH); 7.19–7.29 m , 4 H (CArH); 7.32–7.42 m , 10 H
CPh H). 1 C NMR: 38.4 (CH ); 53.3 (CH); 55.3 (OCH ); 80.5 (CHO-); 123.2 q, 2 C (CF ), JCF
3
1
=
(
2
3
3
2
1
88; 124.8 (CArH); 125.8 (CArH); 126.6 (CArH); 127.3 (CArH); 127.8 (CPh H); 128.3 (CPh H);
29.5 (CPh H); 131.8 (CPh ); 140.0 (CAr); 140.4 (CAr); 166.6, 2 C (C=O); quartern ary C2 atom of
propan oic acid residue was n ot foun d due to low in ten sity an d splittin g by CF group.
3
1
9
1
2
3
F NMR: –72.3, s. Mon oester 8c: H NMR: 2.86 dd, 1 H, JHH = 15.5, JHH = 4.3 (cis-3′-CHH);
.94 dd, 1 H, JHH = 17.2, JHH = 1.9 (cis-3-CHH); 3.32 dd, 1 H, 2J
2
3
= 17.2, JHH = 6.0
3
2
(
1
6
1
HH
trans-3′-CHH); 3.40 q, 3 H, 5J = 1.1 (OCH ); 3.43–3.51 m , 1 H (1′-CH); 3.58 dd, 1 H, JHH
2
=
=
HF
3
3
3
= 6.3, JHH = 2.2 (1-CH); 4.44 dt, 1 H, 3J
3
6.7,
J
= 6.2 (trans-3-CHH); 3.79 dd, 1 H, J
HH
HH
HH
.6 (d), JHH = 4.3 (t) (2′-CHOH-); 5.42 dt, 1 H, 3J
3
= 6.2 (d), JHH = 2.3 (t) (2-CHO-); 6.98 d,
H, JHH = 7.7 (CArH); 7.08–7.48 m , 12 H (CArH + CPh H). C NMR could n ot be assign ed
from th e m ixtu re du e to h igh com plexity of sign als. F NMR: –72.0, s. Mon oester 8d :
H NMR: 2.83 dd, 1 H, JHH = 15.5, JHH = 4.8 (cis-3′-CHH); 3.04 dd, 1 H, JHH = 16.7, JHH = 1.9
3
HH
3
13
1
9
1
2
3
2
3
cis-3-CHH); 3.25 dd, 1 H, JHH = 15.5, JHH = 6.4 (trans-3′-CHH); 3.37 q, 3 H, 5J
2
3
= 1.1
HF
(
2
3
(
1
OCH ); 3.43–3.51 m , 1 H (1′-CH); 3.58 dd, 1 H, JHH = 16.7, JHH = 6.2 (trans-3-CHH); 3.79 dd,
3
H, JHH = 6.3, JHH = 2.2 (1-CH); 4.31 q, 1 H, 3J
3
3
= 6.6 (2′-CHOH-); 5.39 dt, 1 H, JHH = 6.2
= 1.9 (t) (2-CHO-); 6.92 d, 1 H, JHH = 7.2 (CArH); 7.08–7.48 m , 12 H (CArH + CPh H).
C NMR cou ld n ot be assign ed from th e m ixtu re d u e to h igh com p lexity of sign als.
F NMR: –72.0, s.
3
HH
d), 3J
3
(
1
HH
3
1
9
*
*
*
*
(
1R ,1′S ,2R ,2′S )-1,1′-Biin dan e-2,2′-diyl Dim esylate (6)
*
*
*
*
To (1R ,1′S ,2R ,2′S )-1,1′-biin dan e-2,2′-diol (4a; 1.00 g, 3.76 m m ol) an d an h ydrous dich loro-
m eth an e (15 m l), trieth ylam in e (1.36 m l, 9.76 m m ol) was added dropwise wh ile stirrin g an d
coolin g th e m ixture to 0 °C. After 15-m in stirrin g, m esyl ch loride was added dropwise an d
th e m ixture was stirred at 0 °C for 2.5 h . Th e reaction m ixture was th en quen ch ed by addi-
tion of saturated NH Cl (15 m l). CH Cl (15 m l) was added, organ ic layer was separated an d
4
2
2
aqueous layer was extracted with CH Cl (3 × 20 m l). Com bin ed extracts were dried over an -
2
2
h ydrous Na SO an d th e solven t was rem oved on a vacuum rotary evaporator. Pure
2
4
dim esylate 6 (1.462 g, 79.7%, wh ite crystals, m .p. 167–168 °C) was obtain ed by colum n
1
ch rom atograph y (silica, eluen t h exan e/CH Cl /m eth an ol 24:24:1, R 0.20). H NMR: 3.05 s,
2
2
F
2
= 17.7, JHH = 4.7 (cis-CHH); 3.28 dd, 2 H, 2JHH = 17.7, JHH
3
3
6
6
2
H (CH SO ); 3.13 dd, 2 H,
J
=
=
3
2
HH
.9 (trans-CHH); 4.06 d, 2 H, JHH = 2.2 (CH); 5.28 ddd, 2 H, JHH = 6.9, 3JHH = 4.7, 3J
3
3
HH
.2 (CHO-); 6.75 d, 2 H, 3JHH = 7.4; 7.12 t, 2 H, JHH = 7.4; 7.19–7.28 m , 4 H. C NMR: 38.5
3
13
(
(
CH ); 39.5 (CH ); 54.0 (CH); 83.1 (CHO-); 124.3 (CArH); 124.8 (CArH); 127.5 (CArH); 128.1
2 3
CArH); 139.8 (CAr); 149.8 (CAr). IR (CHCl ): 903, 937, 960, 991, 1175, 1334, 1360. For
3
C20H22O6S2 (422.5) calculated: 56.85% C, 5.25% H, 15.18% S; foun d: 56.84% C, 5.27% H,
1
5.31% S.
RESULTS AND DISCUSSION
Dien e 1 was prepared18 by reductive couplin g of cyclopen tan on e with
am algam ated Mg an d TiCl followed by deh ydration with acetic an h y-
4
1
9
20
dride . 1,1′-Biin den e was obtain ed by oxidative couplin g of in den e with
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

1
618
Kvíčala, Baszczyňski, Krupková, Stránská:
an h ydrous CuCl . However, we foun d th at subsequen t isom erization of
2
1
,1′-biin den e to 3,3′-biin den e (2) with trieth ylam in e in pyridin e resulted in
form ation of polym eric products. Moreover, in rem ovin g last traces of pyri-
2
5
din e, substan tial isom erization to th e side product, in dan yliden ein dan e ,
took place. Hen ce, we substituted pyridin e with dich lorom eth an e an d ob-
tain ed dien e 2 of m uch h igh er quality.
To study th e scope an d lim itation s of h ydroboration of cyclic dien es 1, 2
we ch ose th ree stan dard ach iral h ydroboration reagen ts with differen t level
of steric h in dran ce, i.e. boran e, th exylboran e an d 9-BBN. To study
en an tioselectivity of h ydroboration , we also in cluded (–)-isopin ocam ph eyl-
boran e. In th e case of th is reagen t an d dien e 1, we also varied th e reagen t
ratio an d reaction tem perature. Before usin g th e above reagen ts, we per-
form ed h ydroboration s of a m odel com poun d, 2-m eth ylbut-1-en e, to verify
th eir reactivity an d, in th e case of (–)-isopin ocam ph eylboran e, stereo-
selectivity.
In th e course of h ydroboration of dien es 1 or 2, four n ew stereogen ic cen -
tres are form ed. Hydroboration is well kn own to proceed both regio-
selectively an d stereoselectively. Th e regioselectivity depen ds on steric
h in dran ce of th e reagen t; for sterically well-accesible alken es, bulky re-
agen ts such as 9-BBN are gen erally recom m en ded26. In deed, with th e excep-
tion of dien e 1 an d boran e as th e reagen t, all h ydroboration s proceeded
exclusively in a regioselective way. Moreover, all h ydroboration s are kn own
to proceed with a syn-stereoselectivity. Hen ce, on ly two diastereom eric
products are form ed in h ydroboration an d, con sequen tly, due to th e
stereoselectivity of th e oxidative treatm en t of boran es form ed, on ly two
diastereoisom eric diols, meso-isom ers 3a, 4a an d rac-isom ers 3b, 4b, were
form ed (Sch em e 1).
Quite surprisin gly, we foun d th at in all cases th e correspon din g meso-iso-
m ers were form ed preferen tially (Table I). No products were obtain ed from
both dien es 1 an d 2 if 9-BBN was used, probably due to excessive steric h in -
dran ce (run s 9, 13). In gen eral, th e excess of th e un desired meso-isom er was
h igh er wh en m on osubstituted boran es (th exylboran e, (–)-isopin ocam ph eyl-
boran e) were em ployed com pared with un substituted boran e (run s 1–3,
1
0–12). Reaction tem perature did n ot seem to in fluen ce sign ifican tly th e ra-
tio of products form ed (run s 3–6). On th e oth er h an d, we foun d th at at
least som e racem ic diol 3b was form ed if th e am oun t of reagen t was m in i-
m ized; h owever, th is was accom pan ied by a sign ifican t drop of th e yield
(
run 8).
Th e structure of diols 3a, 3b was assign ed accordin g to th e publish ed
NMR spectra. In th e case of meso-diol 3a, th e upgraded in form ation is in -
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

Hydroboration of 1,1′-Bi(cyclopent-1-ene) and 3,3′-Biindene
1619
SCHEME 1
TABLE I
Hydroboration of dien es 1 an d 2
Boran ea
Tem p., °C Tim e, h Yield , %
b
meso/racc
Run
Dien e
1
2
1
1
1
1
1
1
1
1
1
2
2
2
2
BH3
25
0
20
14
136
24
18
2
49.7
40.0
50.4
59.3
50.6
53.6
50.9
32.9
0
82:18
93:7
th exylboran e
3
(–)-isopin ocam ph eylboran e
(–)-isopin ocam ph eylboran e
(–)-isopin ocam ph eylboran e
(–)-isopin ocam ph eylboran e
(–)-isopin ocam ph eylboran e
(–)-isopin ocam ph eylboran e
9-BBN
–70
–25
0
>95:5
>95:5
>95:5
>95:5
>95:5
74:26
4
5
6
25
25
25
25
25
25
25
25
7d
8e
9
2
18
20
20
20
24
20
1
1
1
1
0
1
2
3
BH3
91.8
62.1
74
73:27
82:18
85:15
th exylboran e
(–)-isopin ocam ph eylboran e
9-BBN
0
a
m ol of boran e per m ol of substrate used; isolated yield of th e diol m ixture; c deter-
b
1
1
d
e
m in ed by H NMR; 2 m ol/m ol used; 0.5 m ol/m ol used.
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

1
620
Kvíčala, Baszczyňski, Krupková, Stránská:
cluded. For th e rac-diol, th e overlapped sign als of CH an d CH groups were
2
assign ed usin g th e gHSQC m eth od.
1
6
In ref. , on ly on e diastereoisom er of biin dan ediol 4 was described (th e
m ajor on e) an d assign ed arbitrarily th e (1S,1′S,2S,2′S) con figuration (in cor-
1
6
rectly described as 1R,1′R,2S,2′S in ref. ). We isolated both diastereoisom ers
a, 4b an d to con firm th e origin al assigm en t un equivocally, we tran s-
form ed th em in to th e correspon din g Mosh er’s esters 5 usin g th e m eth odol-
4
2
4
ogy described in ref.
To our surprise, we foun d th at th e m ajor stereoisom er 4a form s on ly on e
1
diester 5a, wh ich lacks th e origin al C -sym m etry (Sch em e 2). In th e H NMR
2
spectra of diester 5a, two sets of in dan e rin g sign als could be observed. In
con trast to th e diastereoisom eric m ixture 5b, 5c, th e two CH groups con -
n ectin g both in dan e un its of diester 5a are coupled (as was con firm ed by
gCOSY experim en t) con n ectin g th e wh ole biin dan e spin system .
SCHEME 2
In agreem en t with th e previous fin din g, th e m in or, so far un kn own
stereoisom er 4b afforded, on th e reaction with ch loride 7, two C -sym m et-
2
ric diastereoisom eric diesters 5b, 5c. Wh ereas we were able to isolate pure
diester 5b in a m in ute am oun t, diester 5c was iden tified in its en rich ed
1
6
m ixture with diester 5b (Sch em e 3). Th us, th e origin al assign m en t is erro-
n eous, th e structure 4a correspon ds to th e meso-stereoisom er an d th e m uch
m ore valuable rac-stereoisom er is th e m in or product 4b. Hydroboration of
biin den e 2 h en ce proceeds with sim ilar stereoch em ical outcom e as th e
h ydroboration of dien e 1. Alon g with diesters 5a–5c, m ixtures of th e corre-
spon din g m on oesters 8a, 8b (from meso-diol 4a) an d 8c, 8d (from rac-diol
4
b) were obtain ed as by-products.
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

Hydroboration of 1,1′-Bi(cyclopent-1-ene) and 3,3′-Biindene
1621
SCHEME 3
Th e absolute con figuration of diesters 5 an d m on oesters 8 was estim ated
1
24,27
based on careful an alysis of H NMR spectra. Th e publish ed
em pirical
observation s for various esters of Mosh er’s acid sh owed th at an idealized
picture can be con structed in wh ich th e trifluorom eth yl groups eclipses th e
carbon yl group of Mosh er’s ester an d h ydrogen of th e ch iral cen tre studied.
Ph en yl group of th e ester m oiety th en sh ields h ydrogen s of on e vicin al CH
or CH group m ore th an th e oth er (Fig. 1).
2
We used ch loride of Mosh er’s acid 7 with th e (S)-con figuration an d, con -
sequen tly, esters with (R)-con figuration were form ed (due to a ch an ge in
th e priority of substituen ts on ch iral carbon of th e esters). Hen ce,
biin dan ediol m oieties with th e probable (1R,2R)-con figuration could be
1
foun d in th e H NMR spectra on th e basis of m ore sh ielded (upfield, lower
ppm values) CH2 group sign als of th e cyclopen tan e rin g, wh ereas th ose
with (1S,2S)-con figuration were ch aracterized by th e m ore sh ielded CH
group (con n ectin g th e two cyclopen tan e rin gs) sign als. For illustration , th e
differen ces in sh ifts between th e 1R,2R an d 1S,2S cen tres of th e th ree corre-
spon din g h ydrogen s are listed in Table II.
FIG. 1
Estim ation of absolute con figuration of esters 5, 8 from 1H NMR spectra
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

1
622
Kvíčala, Baszczyňski, Krupková, Stránská:
In th e case of n on -sym m etrical diester 5a an d in th e case of m on oesters
a–8d th e estim ation of con figuration was rath er straigh tforward in agree-
8
2
7
1
m en t with ref. However, in H NMR spectra of C -sym m etric diesters, th e
2
sh ieldin g of both CH an d CH groups was h igh er for on e diastereoisom er.
2
We decided to estim ate th e probable absolute con figuration of diesters 5b,
5
c based on th e sh ift of th e cis-h ydrogen of th e CH group, as th is sh ould
2
be less in fluen ced by con form ation al ch an ges of th e m olecule th an th e in -
n er h ydrogen of th e C–H group lin kin g both biin dan e un its.
Surprisin gly, diol 4b prepared by h ydroboration of dien e 2 with th e
ch iral reagen t, (–)-isopin ocam ph eylboran e (Table I, run 12), afforded n early
equim olar am oun ts of diesters 5b, 5c an d on ly sm all excess of m on oester
8
d over 8c, wh ich is far from th e publish ed en an tioselectivity for ch iral
h ydroboration of an alogous dien e 1. In deed, m easurem en ts of optical rota-
tion of diol 4b con firm ed th at n early a racem ic m ixture of en an tiom ers was
form ed by ch iral h ydroboration as n o rotation was observed.
To allow furth er tran sform ation s of diols 4, we reacted meso-diol 4a with
m esyl ch loride an d prepared th e correspon din g dim esylate 6 in a good
yield (Sch em e 4).
TABLE II
1
H NMR sh ifts of CH2 an d CH groups in diesters 5 an d m on oesters 8
cis-CHH
1S,2S
trans-CHH
CH
Esters
1
R,2R
RR – SS
1R,2R 1S,2S
RR – SS
1R,2R 1S,2S RR – SS
5
a
2.81
2.97
2.85
2.94
2.94
3.03
2.97
3.04
–0.13
–0.06
–0.12
–0.10
3.19
3.60
3.25
3.58
3.26
3.59
3.34
3.58
–0.07
0.01
–0.09
0
3.84
3.41
3.91
3.79
3.81
3.49
3.84
3.79
0.03
–0.08
0.07
0
5
8
8
b/5c
a/8b
c/8d
SCHEME 4
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

Hydroboration of 1,1′-Bi(cyclopent-1-ene) and 3,3′-Biindene
1623
Sin gle-crystal X-ray an alysis of dim esylate 6 served as furth er con firm a-
tion of meso-structure of th e startin g diol 4a (Fig. 2). CCDC 619802 con -
tain s th e supplem en tary crystallograph ic data for th is paper. Th ese data can
be obtain ed free of ch arge via www.ccdc.cam .ac.uk/con ts/retrievin g.h tm l
(
or from th e Cam bridge Crystallograph ic Data Cen tre, 12, Un ion Road,
Cam bridge, CB2 1EZ, UK; fax: +44 1223 336033; or deposit@ccdc.cam .ac.uk).
High ly preferen tial form ation of th e meso-isom ers of diols 3a, 4a regard-
less of th e reagen t, its excess an d reaction tem perature is rath er surprisin g.
Negative experim en ts with 9-BBN an d an alogous reactivity of th exylboran e
an d boran e h in t th at th e observed stereoselectivity is n ot caused by prefer-
en tial form ation of in term ediate borolan es. To un derstan d m ore th e rea-
son s we decided to perform a sh ort th eoretical study on dien es 1, 2. We
logically en vision ed th e secon d h ydroboration step as th e key step for th e
stereoselectivity an d th us th e com plexes 9a, 9b, 10a, 10b of m on oh ydro-
borated dien es with secon d boran e m olecule as th e key objects of study. As
eth ereal solven t was used in experim en ts, we m icrosolvated th e boran e
m olecule with on e m olecule of sim ulated solven t, dim eth yl eth er (DME).
Due to efficien cy reason s, we em ployed th e DFT m eth od usin g secon d-
gen eration h ybrid fun ction al PBE1PBE (also n am ed PBE0; th is em pirical-
param eter-free fun ction al h as im proved description of van der Waals com -
2
8
plexes com pared with tradition al B3LYP fun ction al ; an oth er advan tage is
2
9
its im plem en tation in both com m ercial Gaussian 03W
PCGAMESS
an d free of ch arge
3
0,31
program packages) togeth er with 6-31G(d) Gaussian basis
set, a m in im al set appropriate for DFT calculation s. In th is case, all calcula-
tion s were perform ed with Gaussian 03W 29 program package. We first care-
FIG. 2
*
*
*
*
ORTEP plot of (1R ,1′S ,2R ,2′S )-1,1′-biin dan e-2,2′-diyl dim esylate (6, CCDC 619802)
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

1
624
Kvíčala, Baszczyňski, Krupková, Stránská:
fully in vestigated th e con form ation al space of all four com plexes to fin d
global m in im a. In som e cases, very flat in flexion s were observed for th e
studied com plexes in stead of true m in im a. Neverth eless, th e correspon din g
products of h ydroboration (true m in im a in all cases) sh ow an alogous stabil-
ity pattern s. Th e geom etries an d relative en ergies of th ese com plexes, 9a
(
precursor of meso-diol 3a), 9b (precursor of rac-diol 3b), 10a (precursor of
meso-diol 4a) an d 10b (precursor of rac-diol 4b), are depicted in Fig. 3.
Complex: 9a
Complex: 9b
Precursor of:
Precursor of:
meso-3a
rac-3b
Relative energy:
Relative energy:
10.2 kJ/mol
0
.0 kJ/mol
Complex: 10a; Precursor of: meso-4a
Complex: 10b; Precursor of: rac-4b
Relative energy: 9.4 kJ/mol
Relative energy: 0.0 kJ/mol
FIG. 3
Calculated equilibrium geom etries an d relative en ergies of h ydroboration in term ediates 9a,
b, 10a, 10b
9
Collect. Czech. Chem. Commun. 2006, Vol. 71, Nos. 11–12, pp. 1611–1626

Hydroboration of 1,1′-Bi(cyclopent-1-ene) and 3,3′-Biindene
1625
In agreem en t with th e experim en tal results, we foun d in both cases th at
com plex precursors 9a, 10a of meso-diols 3a, 4a are m ore favorable by ca.
1
0 kJ/m ol com pared with precursors 9b, 10b of rac-diols 3b, 4b. Th is can be
explain ed by th e fact th at th e cyclopen tan e an d cyclopen ten e rin gs of th e
m on oh ydroborated in term ediates are approxim ately perpen dicular. Th e
con form ers with th e cyclopen ten e rin g double bon d less sh ielded by th e
rin g th en lead to m ore stable com plexes 9a, 10a with secon d m olecule of
boran e wh ich in turn afford meso-diols 3a, 4a after th e stan dard oxidative
work-up.
Th us, we con firm ed both experim en tally an d th eoretically th at th e m ajor
products of h ydroboration /oxidation of cyclic dien es 1, 2 are th e un desired
meso-diols 3a, 4a regardless of th e reagen t, its excess, reaction tem perature
an d tim e. rac-Diols 3b, 4b are form ed as m in or products. Boran e–THF com -
plex is th e h ydroboration reagen t of ch oice for th e preparation of diols 3b,
4
b as it is ch eaper th an oth er reagen ts an d affords a little m ore advan ta-
geous ratio of stereoisom ers. Moreover, th e isolation of th e desired diols 3b,
b is m ore straigh tforward as th e reaction m ixture is n ot con tam in ated
4
with organ ic oxidation products of th e h ydroboration reagen t.
We thank the Grant Agency of the Czech Republic (grant No. 203/03/0496) for financial support
and M. Pojarová, MSc. for determination of the X-ray crystal structure of dimesylate 6.
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