Direct preparation of N-(Alk-1-en-1-yl)carbamates from cyclic ketones and unsubstituted carbamates

Article abstract of DOI:10.1135/cccc20020235

N-(Alk-1-en-1-yl)carbamates bearing an endocyclic carbon-carbon double bond have been prepared by the reaction of unsubstituted carbamates with tetrahydronaphthalen-2-one and chroman-2-one derivatives in the presence of a catalytic amount of 4-methylbenze

Full text of DOI:10.1135/cccc20020235

Preparation of N-(Alk-1-en-1-yl)carbamates
235
DIRECT PREPARATION OF N-(ALK-1-EN-1-YL)CARBAMATES
FROM CYCLIC KETONES AND UNSUBSTITUTED CARBAMATES
1
Philippe DUPAU , Anne-Emmanuelle HAY, Célia ALAMEDA ANGULO,
2
3,
Pierre H. DIXNEUF and Christian BRUNEAU *
Institut de Chimie de Rennes, UMR 6509: CNRS-Université de Rennes,
Organométalliques et Catalyse, Campus de Beaulieu, 35042 Rennes Cedex, France;
1
2
e-mail: philippe.dupau@firmenich.com, pierre.dixneuf@univ-rennes1.fr,
3
christian.bruneau@univ-rennes1.fr
Received April 30, 2001
Accepted Decem ber 17, 2001
N-(Alk-1-en -1-yl)carbam ates bearin g an en docyclic carbon -carbon double bon d h ave been
prepared by th e reaction of un substituted carbam ates with tetrah ydron aph th alen -2-on e an d
ch rom an -2-on e derivatives in th e presen ce of a catalytic am oun t of 4-m eth ylben zen e-
1-sulfon ic acid.
Keyw ord s: N-(Alk-1-en -1-yl)carbam ates; Cyclic keton es; Ch rom en es; Dih ydron aph th alen es;
Am in es; Acid catalysis; En an tioselective h ydrogen ation .
N-(Alk-1-en -1-yl)carbam ates are a class of com poun ds with poten tial in or-
gan ic syn th esis. Th ey can easily be acylated via Friedel–Crafts an d Vilsm eier
reaction s, th ey produce β-am in o alcoh ol derivatives via h ydroboration 1,
an d th ey h ave recen tly been in volved in th e m odification of N-protected
deh ydroam in o acids via oxidation of th eir C=C double bon ds2,3 to produce
fun ction alized α-am in o acid derivatives. Th eir activated double bon d h as
been used to perform [2+2] cycloaddition with h eteroallen es, n am ely
dich loroketen e, to give m odified prolin e com poun ds4, an d to react with
ch rom ium alkoxycarben es to produce optically active spiroketals5. Th e
stereoselective palladium -catalyzed Heck-type reaction of en docyclic
N-(alk-1-en -1-yl)carbam ates with diazon ium tetrafluoroborate h as been
used as a key step in th e syn th esis of pyrrolidin e alkaloids6.
Th e double bon d of deh ydro-N-carbam oyl-α-am in o acids7, an d deh ydro-
N-carbam oyl-β-am in o alcoh ols, acetates an d oxim es8, all of th em bi-
fun ction al com poun ds con tain in g two poten tial ch elatin g groups, h as been
en an tioselectively h ydrogen ated in th e presen ce of rh odium catalysts to af-
ford optically active acyclic α-am in o acid7, an d β-am in o alcoh ol an d
1,2-diam in e8 derivatives. Th e en an tioselective h ydrogen ation of th e C=C
Collect. Czech. Chem. Commun. (Vol. 67) (2002)
doi:10.1135/cccc20020235

236
Dupau et al.:
bon d of a cyclic N-(alk-1-en -1-yl)carbam ate was also perform ed in th e pres-
en ce of a ruth en ium (bin ap) precursor to gen erate optically active
pyrrolidin e derivatives with m oderate en an tioselectivity9. We h ave also
sh own th at 4-m eth ylen e-N-acyloxazolidin on es, wh ich are m em bers of th e
cyclic N-(alk-1-en -1-yl)carbam ate fam ily with th e n itrogen atom in th e
rin g, were h ydrogen ated in th e presen ce of ruth en ium com plexes with very
h igh en an tioselectivity10 providin g a straigh tforward access to both R- an d
S-en an tiom ers of th e very useful acyloxazolidin on e ch iral auxiliaries11
.
More recen tly, cyclic N-(alk-1-en -1-yl)carbam ates bearin g an en docyclic
C=C bon d were also en an tioselectively h ydrogen ated usin g ruth en ium ca-
talysis in a th ree-step con version of cyclic keton es in to optically active
am in es12.
Th e preparation of N-(alk-1-en -1-yl)carbam ates was in itially based on
acylation of en am in es or im in es with ch loroform ates in th e presen ce of a
base4a,13. Th e deh ydration of cyclic N-(1-h ydroxyalkyl)carbam ates pro-
m oted by trifluoroacetic an h ydride/2,6-lutidin e4a,6,14, an d th e sodium
perrh en ate-catalyzed reaction of α-azido keton es with ch loroform ate15 af-
ford cyclic carbam ates bearin g an en docyclic carbon –carbon double bon d.
Cyclic an d acyclic N-(alk-1-en -1-yl)carbam ates h ave been obtain ed by elim i-
n ation of m eth an ol from N-(1-m eth oxyalkyl)carbam ates in th e presen ce of
am m on ium ch loride as acid catalyst1. N-(1-Alkoxycarbon yl-1-en -1-yl)carba-
m ates h ave been obtain ed in good yields from α-ketoesters by th e
acid-catalyzed reaction of prim ary carbam ates in th e presen ce of POCl3
(ref.16), TsOH (refs7b,17) or HCl (ref.7c).
Followin g our objective to tran sform cyclic keton es in to optically active
am in es12,18, we were in terested in sim ple preparation s of N-(alk-1-en -
1-yl)carbam ates. We report h ere a straigh tforward acid-catalyzed syn th esis
of n ew N-(alk-1-en -1-yl)carbam ates by direct con den sation of un substituted
carbam ates with th e un activated cyclic keton es 1, 2 an d 3 accordin g to
Sch em e 1.
RESULTS AND DISCUSSION
As m en tion ed in th e in troduction , th e acid-catalyzed con den sation of
un substituted carbam ates with activated keton es, such as α-ketoesters h as
been kn own , but th e reaction with un activated cyclic keton es h as n ot yet
been reported. Due to th e n ecessity of th e presen ce of an acid catalyst in
th is reaction an d with th e goal of an easy rem oval of th e catalyst, we first
tested th e activity of th e acid ion -exch an ge resin Am berlyst 15, wh ich was
used in th e form ation of en am ides from prim ary am ide an d cyclic ke-
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

Preparation of N-(Alk-1-en-1-yl)carbamates
237
R1
R1
H
O
O
N
OR
TsOH (10 mole %)
refluxing toluene
+
H2N
OR
O
R2
X
R2
X
R3
R3
4-18
R1
H
H
X
R2
H
R3
H
CH2
CH2
O
1
2
3
CH3 CH2CH2COOH
H
OCH3
H
SCHEME 1
TABLE I
Preparation of N-(alk-1-en -1-yl)carbam ates 4–18a
X
R1
H
R2
H
R3
H
R
Carbam ate Yield, %
CH2
Et
4
5
90
93b
78
85
55
50
60
68
66
60
60
50
65
50
64
Me
Bu
6
i-Bu
t-Bu
Ph
7
8
9
Ph CH2
CCl3CH2
Et
10
11
12
13
14
15
16
17
18
CH2
H
Me
H
CH2CH2CO2H
t-Bu
Ph CH2
Et
O
OMe
H
t-Bu
Ph CH2
CH2=CHCH2
a
Gen eral con dition s: keton e (10 m m ol), carbam ate (25 m m ol), TsOH (1 m m ol), refluxin g
b
toluen e, Dean –Stark apparatus, in ert atm osph ere, 20 h . Carbam ate (50 m m ol).
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

238
Dupau et al.:
ton es19, but with out success. Th e activation with a Lewis acid such as
BF3·Et2O also proved to be in efficien t. Fin ally, an efficien t direct prepara-
tion was ach ieved wh en 4-m eth ylben zen e-1-sulfon ic acid was used in
refluxin g toluen e.
Thus, when 10 mmol of 1,2,3,4-tetrahydronaphthalen-2-one 1 and 25 mmol
of eth yl carbam ate were h eated for 20 h un der in ert atm osph ere in th e pres-
en ce of 1 m m ol of TsOH in refluxin g toluen e in a Dean –Stark apparatus,
th e correspon din g N-(alk-1-en -1-yl)carbam ate 4 was isolated in 90% yield
after ch rom atograph y over silica gel.
Un der sim ilar con dition s, th e N-(alk-1-en -1-yl)carbam ates 5–11 were pre-
pared in good yields from prim ary alkyl an d aryl carbam ates (Table I). It
was im portan t to perform th e reaction un der an in ert atm osph ere of n itro-
gen an d to con tin uously rem ove water from th e reaction m ixture. In th e
case of m eth yl carbam ate, 5 equivalen ts were used because of its sublim a-
tion in side th e apparatus. Th e con den sation reaction was also perform ed in
satisfactory yields with th e related tetralon e 2, wh ich con tain s a carboxylic
group as substituen t of th e arom atic rin g, an d th e N-(alk-1-en -1-yl)carba-
m ates 12–14 were isolated in 66, 60 an d 60% yield, respectively (Table I).
Th e gen erality of th e reaction was sh own by th e syn th esis of th e
N-(alk-1-en -1-yl)carbam ates 15–18 from th e ch rom an -2-on e derivative 3
(Table I).
It is noteworthy that only the N-(alk-1-en-1-yl)carbamates with the carbon–
carbon double bon d con jugated with th e arom atic rin g were form ed.
Th ese N-(alk-1-en -1-yl)carbam ates could be isolated as colorless oils or
wh ite solids, but th ey were very air an d m oisture-sen sitive an d h ad to be
kept at 6 °C in a refrigerator, or used as soon as th ey were produced. Th ey
1
sh owed a H NMR sign al for th e vin ylic proton in th e ran ge 6.5–6.8 ppm .
Th e ch aracteristic HC=C–NH–CO2 structure led to th ree sign als in th e 13C
spectra at 100–110 (HC=), 127–133 (C–N) an d 151–154 (C=O) ppm .
Th e carbam ates were tested in en an tioselective h ydrogen ation with th e
goal of producin g optically active am in es. Th e well-kn own Ru(O2CCF3)2-
((R)-bin ap) com plex was in active in th e h ydrogen ation of th e N-(alk-1-en -
1-yl)carbam ates 4–10 derived from 2-tetralin . On th e oth er h an d, th e
N-(alk-1-en -1-yl)carbam ates 15–18 were h ydrogen ated in m eth an ol at 60 °C
un der 10 MPa of h ydrogen in th e presen ce of 1 m ole % of Ru(O2CCF3)2-
((R)-bin ap) as catalyst precursor (Sch em e 2), but th e en an tiom eric excesses
were n ot satisfactory (<25%). Th e best results were obtain ed with th e
N-(alk-1-en -1-yl)carbam ates 12–14, wh ich un der sim ilar con dition s gave
th e correspon din g carbam ates derived from 2-tetralin in 65–88%
en an tiom eric excesses12 (Table II). Th e results sh ow th at th e presen ce of
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

Preparation of N-(Alk-1-en-1-yl)carbamates
239
fun ction al groups on th e bicyclic structure m akes th e h ydrogen ation possi-
ble yieldin g in depen dan ce on th eir n ature an d position , optically-en rich ed
am in e derivatives. As expected, th e am in e h ydroch lorides were obtain ed by
appropriate deprotection m eth ods un der m ild con dition s with out racem -
ization 12
.
In con clusion , we h ave sh own th at th e acid-catalyzed con den sation of
un substituted carbam ates with cyclic keton es provides a straigh tforward
an d selective route to N-(alk-1-en -1-yl)carbam ates. Th ese com poun ds are
suitable precursors for en an tioselective h ydrogen ation affordin g optically
active carbam ates, wh ich can easily be deprotected by well-kn own m eth ods
to produce optically active am in es.
R1
R1
H
H
N
OR
N
OR
H2, 10 MPa, MeOH
*
O
O
Ru(O2CCF3)2((R)-binap)
R2
X
R2
X
R3
(1 mole %)
R3
19-22
12-15
X
O
CH2
CH2
CH2
R1
OCH3
H
H
H
R2
H
R3
H
R
Et
Et
t-Bu
15, 19
12, 20
13, 21
14, 22
CH3 CH2CH2COOH
CH3 CH2CH2COOH
CH3 CH2CH2COOH
PhCH2
SCHEME 2
TABLE II
En an tioselective h ydrogen ation of N-(alk-1-en -1-yl)carbam ates 12–15a
En ecarbam ate
Reaction tim e, h
Carbam ate
Yieldb, %
e.e., %
12
13
14
15
20
48
60
20
20
21
22
19
80
94
95
90
75
65
88
22
a
Gen eral con dition s: carbam ate (1 m m ol), H2 (10 MPa), MeOH (10 m l), catalyst
b
Ru(O2CCF3)2((R)-bin ap) (0.01 m m ol), 50 °C. Isolated yield.
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

240
Dupau et al.:
EXPERIMENTAL
Preparation of N-(Alk-1-en -1-yl)carbam ates
In to a 250 m l flask equipped with a Dean –Stark apparatus, 10 m m ol of keton e, 25 m m ol of
a carbam ate an d 1 m m ol (192 m g) of 4-m eth ylben zen e-1-sulfon ic acid m on oh ydrate were
in troduced un der an in ert atm osph ere of n itrogen . Toluen e (60 m l) was th en added an d th e
m ixture was refluxed for 20 h . After coolin g, 40 m l of toluen e was added an d th e organ ic
ph ase was wash ed th ree tim es with 100 m l of water. Th e organ ic ph ase was th en evaporated
to dryn ess an d th e N-(alk-1-en -1-yl)carbam ates were purified by flash ch rom atograph y on
silica gel with a dieth yl eth er–pen tan e m ixture as eluen t (4 : 1 for 4–11, 2 : 1 for 12–18).
Th e isolated N-(alk-1-en -1-yl)carbam ates were very air-sen sitive an d stored un der n itrogen
at 6 °C.
Ethyl N-(3,4-dihydro-2-naphthyl)carbamate (4). Colorless oil, yield 90%. 1H NMR
(200.130 MHz, CDCl3): 1.27 (t, J = 7.1, 3 H, CH3); 2.40 (t, J = 8.2, 2 H, rin g CH2); 2.86 (t, J =
8.2, 2 H, rin g CH2); 4.17 (q, J = 7.1, 2 H, OCH2); 6.02 (broad s, 1 H, NH); 6.76 (s, 1 H, CH=);
1
6.90–7.15 (m , 4 H arom .). 13C NMR { H} (50.323 MHz, CDCl3): 14.63 (CH3), 27.42 (rin g
CH2), 28.06 (rin g CH2), 52.4 (OCH2), 108.67 (CH=), 125.44 (CH arom .), 125.76 (CH arom .),
126.74 (CH arom .), 127.05 (CH arom .), 132.44 (C quat. =CN), 135.04 (C quat. arom .),
135.31 (C quat. arom .), 153.46 (CO carbam ate). HRMS: calculated for C13H15NO2 [M]+
217.11028, foun d 217.1119.
Methyl N-(3,4-dihydro-2-naphthyl)carbamate (5). Colorless oil, yield 93%. 1H NMR
(200.130 MHz, CDCl3): 2.40 (t, J = 8.1, 2 H, rin g CH2); 2.86 (t, J = 8.1, 2 H, rin g CH2); 3.72
(s, 3 H, OCH3); 6.03 (broad s, 1 H, NH); 6.76 (s, 1 H, CH=); 6.90–7.20 (m , 4 H arom .).
1
13C NMR { H} (50.323 MHz, CDCl3): 27.39 (rin g CH2), 28.04 (rin g CH2), 61.3 (OCH3),
108.82 (CH=), 125.52 (CH arom .), 125.79 (CH arom .), 126.75 (CH arom .), 127.06 (CH
arom .), 132.44 (C quat. =CN), 134.94 (C quat. arom .), 135.13 (C quat. arom .), 153.85 (CO
carbam ate). HRMS: calculated for C12H13NO2 [M]+ 203.09463, foun d 203.0940.
Butyl N-(3,4-dihydro-2-naphthyl)carbamate (6). Colorless oil, yield 78%. 1H NMR
(200.130 MHz, CDCl3): 0.93 (t, J = 7.3, 3 H, CH3); 1.20–1.50 (m , 2 H, CH2); 1.50–1.80 (m ,
2 H, CH2); 2.40 (t, J = 8.2, 2 H, rin g CH2); 2.86 (t, J = 8.2, 2 H, rin g CH2); 4.12 (q, J = 7.3,
2 H, OCH2); 6.05 (broad s, 1 H, NH); 6.77 (s, 1 H, CH=); 6.90–7.15 (m , 4 H arom .). HRMS:
calculated for C15H19NO2 [M]+ 245.14158, foun d 245.1409.
Isobutyl N-(3,4-dihydro-2-naphthyl)carbamate (7). Colorless oil, yield 85%. 1H NMR
(200.130 MHz, CDCl3): 0.94 (d, J = 6.8, 6 H, 2 CH3); 1.94 (h ept, J = 6.8, 1 H, CH); 2.41 (t, J =
8.2, 2 H, rin g CH2); 2.86 (t, J = 8.2, 2 H, rin g CH2); 3.90 (d, J = 6.8, 2 H, OCH2); 6.05
1
(broad s, 1 H, NH); 6.76 (s, 1 H, CH=); 7.25–7.40 (m , 4 H arom .). 13C NMR { H} (50.323
MHz, CDCl3): 19.12 (2 CH3), 27.58 (rin g CH2), 27.98 (CH), 28.00 (rin g CH2), 71.44 (OCH2),
108.63 (CH=), 125.43 (CH arom .), 125.77 (CH arom .), 126.72 (CH arom .), 126.99 (CH
arom .), 132.35 (C quat. =CN), 134.93 (C quat. arom .), 135.00 (C quat. arom .), 153.35 (CO
carbam ate). HRMS: calculated for C15H19NO2 [M]+ 245.14158, foun d 245.1409.
tert-Butyl N-(3,4-dihydro-2-naphthyl)carbamate (8). Colorless oil, yield 55%. 1H NMR
(200.130 MHz, CDCl3): 1.48 (s, 9 H, t-Bu); 2.36 (t, J = 8.2, 2 H, rin g CH2); 2.85 (t, J = 8.2,
2 H, rin g CH2); 5.87 (broad s, 1 H, NH); 6.76 (s, 1 H, CH=); 6.90–7.20 (m , 4 H arom .).
HRMS: calculated for C15H19NO2 [M]+ 245.14158, foun d 245.1409.
Phenyl N-(3,4-dihydro-2-naphthyl)carbamate (9). W h ite solid, yield 50%. 1H NMR
(200.130 MHz, CDCl3): 2.49 (t, J = 8.2, 2 H, rin g CH2); 2.91 (t, J = 8.2, 2 H, rin g CH2); 6.36
Collect. Czech. Chem. Commun. (Vol. 67) (2002)

Preparation of N-(Alk-1-en-1-yl)carbamates
241
(broad s, 1 H, NH); 6.82 (s, 1 H, CH=); 6.90–7.30 (m , 7 H arom .); 7.30–7.50 (m , 2 H arom .).
1
13C NMR { H} (50.323 MHz, CDCl3): 27.19 (rin g CH2), 28.04 (rin g CH2), 109.95 (CH=),
121.78 (2 × CH arom .), 125.84 (CH arom .), 125.86 (CH arom .), 126.03 (CH arom .), 126.84
(CH arom.), 127.15 (CH arom.), 129.54 (2 × CH arom.), 132.58 (C quat. =CN), 134.70 (2 × C quat.
arom .), 150.62 (C quat. arom .), 151.48 (CO carbam ate). For C17H15NO2 (265.3) calculated:
76.96% C, 5.70% H, 5.28% N; foun d: 76.85% C, 5.81% H, 5.35% N.
Benzyl N-(3,4-dihydro-2-naphthyl)carbamate (10). Colorless oil, yield 60%. 1H NMR
(200.130 MHz, CDCl3): 2.39 (t, J = 8.2, 2 H, rin g CH2); 2.86 (t, J = 8.2, 2 H, rin g CH2); 5.15
(s, 2 H, OCH2); 6.08 (broad s, 1 H, NH); 6.79 (s, 1 H, CH=); 6.90–7.15 (m , 4 H arom .);
1
7.25–7.40 (m , 5 H arom .). 13C NMR { H} (50.323 MHz, CDCl3): 27.49 (rin g CH2), 28.01 (rin g
CH2), 67.09 (OCH2), 108.95 (CH=), 125.55 (CH arom .), 125.84 (CH arom .), 126.76 (CH
arom .), 127.04 (CH arom .), 128.43 (2 × CH arom .), 128.48 (CH arom .), 128.72 (2 × CH
arom .), 132.40 (C quat. =CN), 134.85 (2 × C quat. arom .), 136.05 (C quat. arom .), 152.94
(CO carbam ate). HRMS: calculated for C18H17NO2 [M]+ 279.12593, foun d 279.1262.
2,2,2-Trichloroethyl N-(3,4-dihydro-2-naphthyl))carbamate (11). Colorless oil, yield 68%.
1H NMR (200.130 MHz, CDCl3): 2.46 (t, J = 8.2, 2 H, rin g CH2); 2.89 (t, J = 8.2, 2 H, rin g
CH2); 4.77 (s, 2 H, OCH2); 6.31 (broad s, 1 H, NH); 6.79 (s, 1 H, CH=); 6.90–7.15 (m , 4 H
1
arom .). 13C NMR { H} (50.323 MHz, CDCl3): 27.21 (rin g CH2), 27.98 (rin g CH2), 74.57
(OCH2), 95.36 (C quat. CCl3), 110.33 (CH=), 125.99 (CH arom .), 126.04 (CH arom .), 126.85
(CH arom .), 127.17 (CH arom .), 132.54 (C quat. =CN), 134.32 (C quat. arom .), 134.44
(C quat. arom .), 151.21 (CO carbam ate). HRMS: calculated for
318.99336, foun d 318.9946.
C
13H12NO2Cl3 [M]+
3-[6-(Ethoxycarbonamido)-2-methyl-7,8-dihydro-1-naphthyl]propanoic acid (12). Wh ite solid,
yield 66%. 1H NMR (200.130 MHz, CDCl3): 1.27 (t, J = 7.1, 3 H, CH3 carbam ate); 2.29 (s,
3 H, CH3); 2.30–2.60 (m , 4 H, rin g CH2 + CH2); 2.80–3.10 (m , 4 H, rin g CH2 + CH2); 4.17 (q,
J = 7.1, 2 H, OCH2); 6.13 (broad s, 1 H, NH); 6.69 (s, 1 H, CH=); 6.81 (d, J = 7.7, 1 H arom .);
1
6.93 (d, J = 7.7, 1 H arom .). 13C NMR { H} (50.323 MHz, CDCl3): 14.61 (CH3 carbam ate),
19.91 (CH3), 24.45 (2 × CH2), 27.41 (rin g CH2), 33.73 (rin g CH2), 61.52 (OCH2), 109.40
(CH=), 124.55 (CH arom .), 128.56 (CH arom .), 130.51 (C quat. =CN), 133.26 (C quat.
arom .), 133.79 (C quat. arom .), 133.98 (C quat. arom .), 135.16 (C quat. arom .), 153.76 (CO
carbam ate), 179.01 (COOH). For C17H21NO4 (303.4) calculated: 67.31% C, 6.98% H,
4.62% N; foun d: 67.21% C, 6.89% H, 4.70% N.
3-[6-(tert-Butoxycarbonamido)-2-methyl-7,8-dihydro-1-naphthyl]propanoic acid (13). Wh ite
solid, yield 60%. 1H NMR (200.130 MHz, CDCl3): 1.48 (s, 9 H, t-Bu); 2.28 (s, 3 H, CH3);
2.32–2.47 (m , 4 H, rin g CH2 + CH2); 2.81–3.05 (m , 4 H, rin g CH2 + CH2); 6.17 (broad s, 1 H,
NH); 6.68 (s, 1 H, CH=); 6.78 (d, J = 8.0, 1 H arom .); 6.91 (d, J = 8.0, 1 H arom .). For
C
19H25NO4 (331.4) calculated: 68.86 % C, 7.60% H, 4.23 % N; foun d: 69.05% C, 7.65% H,
4.15% N.
3-[6-(Benzyloxycarbonamido)-2-methyl-7,8-dihydro-1-naphthyl]propanoic acid (14). W h ite
solid, yield 60%. 1H NMR (200.130 MHz, CDCl3): 2.29 (s, 3 H, CH3); 2.34–2.50 (m , 4 H, rin g
CH2 + CH2); 2.80–3.05 (m , 4 H, rin g CH2 + CH2); 5.15 (s, 2 H, OCH2); 6.26 (broad s, 1 H,
NH); 6.71 (s, 1 H, CH=); 6.81 (d, J = 7.7, 1 H arom .); 6.94 (d, J = 7.7, 1 H arom .); 7.36 (broad
1
s, 5 H arom .). 13C NMR { H} (50.323 MHz, CDCl3): 19.91 (CH3), 24.42 (2 × CH2), 27.41 (rin g
CH2), 33.68 (rin g CH2), 67.22 (OCH2), 109.53 (CH=), 124.60 (CH arom .), 128.40 (2 × CH
arom .), 128.48 (CH arom .), 128.60 (CH arom .), 128.71 (2 × CH arom .), 130.50 (C quat.
=CN), 133.16 (C quat. arom .), 133.74 (C quat. arom .), 133.89 (C quat. arom .), 135.15
(C quat. arom .), 135.99 (C quat. arom .), 153.24 (CO carbam ate), 178.98 (COOH). For
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Dupau et al.:
C22H23NO4 (365.4) calculated: 72.31% C, 6.34% H, 3.83% N; foun d: 72.05% C, 6.25% H,
3.85% N.
Ethyl N-(5-methoxychromen-3-yl)carbamate (15). W h ite solid, yield 50%. 1H NMR
(200.130 MHz, CDCl3): 1.26 (t, J = 7.1, 3 H, CH3); 3.78 (s, 3 H, OCH3); 4.15 (q, J = 7.1, 2 H,
OCH2 carbam ate); 4.83 (s, 2 H, rin g CH2); 6.25 (broad s, 1 H, NH); 6.43 (d, J = 8.2, 1 H
arom .); 6.46 (d, J = 8.2, 1 H arom .); 6.54 (s, 1 H, CH=); 6.96 (t, J = 8.2, 1 H arom .). For
C
13H15NO4 (249.3) calculated: 62.64% C, 6.07% H, 5.62% N; foun d: 62.80% C, 6.12% H,
5.78% N.
tert-Butyl N-(5-methoxychromen-3-yl)carbamate (16). W h ite solid, yield 65%. 1H NMR
(200.130 MHz, CDCl3): 1.46 (s, 9 H, t-Bu); 3.78 (s, 3 H, OCH3); 4.78 (s, 2 H, OCH2); 6.03
(broad s, 1 H, NH); 6.43 (d, J = 8.2, 1 H arom .); 6.45 (d, J = 8.2, 1 H arom .); 6.54 (s, 1 H,
1
CH=); 6.95 (t, J = 8.2, 1 H arom .). 13C NMR { H} (50.323 MHz, CDCl3): 28.28 (3 × CH3,
t-Bu), 55.67 (OCH3), 65.36 (OCH2), 81.10 (C quat. t-Bu), 100.10 (CH=), 104.05 (CH arom .),
108.46 (CH arom .), 112.44 (C quat. arom .), 126.96 (CH arom .), 128.31 (C quat. =CN),
152.42 (C quat. arom .), 152.69 (CO carbam ate), 154.86 (C quat. arom .). HRMS: calculated
for C15H19NO4 [M]+ 277.13141, foun d 277.1303.
Benzyl N-(5-methoxychromen-3-yl)carbamate (17). W h ite solid, yield 50%. 1H NMR
(200.130 MHz, CDCl3): 3.78 (s, 3 H, OCH3); 4.83 (s, 2 H, rin g CH2); 5.13 (s, 2 H, OCH2
carbam ate); 6.26 (broad s, 1 H, NH); 6.43 (d, J = 8.2, 1 H arom .); 6.46 (d, J = 8.2, 1 H arom .);
1
6.56 (s, 1 H, CH=); 6.97 (t, J = 8.2, 1 H arom .); 7.35 (broad s, 5 H arom .). 13C NMR { H}
(50.323 MHz, CDCl3): 55.69 (OCH3), 65.18 (OCH2), 67.29 (OCH2), 100.86 (CH=), 104.19
(CH arom .), 108.62 (CH arom .), 112.50 (C quat. arom .), 127.23 (CH arom .), 127.91 (C quat.
=CN), 128.25 (CH arom .), 128.40 (2 × CH arom .), 128.71 (2 × CH arom .), 136.06 (C quat.
arom .), 152.59 (C quat. arom .), 153.63 (CO carbam ate), 155.04 (C quat. arom .). For
C
15H19NO4 (277.3) calculated: 64.97% C, 6.91% H, 5.05% N; foun d 65.11% C, 6.82% H,
4.98% N.
Allyl N-(5-methoxychromen-3-yl)carbamate (18). W h ite solid, yield 64%. 1H NMR
(200.130 MHz, CDCl3): 3.78 (s, 3 H, OCH3); 4.59 (dt, J = 6.1 an d 1.4, 2 H, allyl OCH2); 4.83
(s, 2 H, OCH2); 5.20–5.36 (m , 2 H, =CH2); 5.60–5.80 (m , 1 H, allyl CH=); 6.25 (broad s, 1 H,
NH); 6.43 (d, J = 8.2, 1 H arom .); 6.45 (d, J = 8.2, 1 H arom .); 6.55 (s, 1 H, CH=); 6.97 (t, J =
8.2, 1 H arom .). For C14H15NO4 (261.3) calculated: 64.36% C, 5.79% H, 5.36% N; foun d:
64.51% C, 5.65% H, 5.22% N.
Procedure for En an tioselective Hydrogen ation
In a 125 m l stain less steel autoclave were in troduced un der in ert atm osph ere 1 m m ol of
N-(alk-1-en -1-yl)carbam ate, 0.01 m m ol of Ru(O2CCF3)2((R)-bin ap) an d 10 m l of m eth an ol.
Th e autoclave was th en flush ed th ree tim es with h ydrogen an d pressurized to 10 MPa. After
reaction , th e crude m ixture was evaporated an d th e con version was determ in ed by 1H NMR.
After rem oval of th e organ om etallic residues, by filtration on silica gel, th e en an tiom eric ex-
cess was m easured by HPLC with a ch iral colum n (Ch iralcel OD 25 cm ) with a h exan e–
isopropan ol (85 : 15) m ixture as eluen t.
Ethyl N-(5-methoxychromen-3-yl)carbamate (19). W h ite solid, yield 90%. 1H NMR
(200.130 MHz, CDCl3): 1.25 (t, J = 7.1, 3 H, CH3); 2.66 (d, J = 17.4, 1 H, rin g CH2); 2.85 (dd,
J = 17.4 an d 5.6, 1 H, CH2) ; 3.78 (s, 3 H, OCH3); 4.02–4.25 (m , 5 H, rin g OCH2 + OCH2Me);
4.81 (broad s, 1 H, NH); 6.42 (d, J = 8.3, 1 H arom .); 6.47 (d, J = 8.3, 1 H arom .); 7.07 (t, J =
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Preparation of N-(Alk-1-en-1-yl)carbamates
243
8.3, 1 H arom .). For C13H17NO4 (251.3) calculated: 62.14% C, 6.82% H, 5.57% N; foun d:
62.00% C, 6.75% H, 5.68% N.
3-[6-(Ethoxycarbonamido)-2-methyl-5,6,7,8-tetrahydro-1-naphthyl]propanoic acid (20). Wh ite
solid, yield 80%. 1H NMR (200.130 MHz, CDCl3): 1.22 (t, J = 7.1, 3 H, CH3); 1.65–1.90 (m ,
1 H, rin g CH2); 195–2.20 (m , 1 H, rin g CH2); 2.29 (s, 3 H, CH3); 2.35–2.52 (m , 2 H, CH2);
2.66 (dd, J = 16.0 an d 8.1, 1 H, rin g CH2); 2.72–3.00 (m , 4 H, rin g CH2 + CH2); 3.07 (dd, J =
16 an d 4.8, 1 H, rin g CH2); 3.76–4.02 (m , 1 H, CHN); 4.10 (q, J = 7.1, OCH2); 4.66 (broad s,
1 H, NH); 6.83 (d, J = 8.0, 1 H arom .); 6.94 (d, J = 8.0, 1 H arom .). 13C NMR {1H}
(50.323 MHz, CDCl3): 14.67 (CH3), 19.54 (CH3), 24.42 (2 × CH2), 29.24 (rin g CH2), 33.13
(rin g CH2), 36.49 (rin g CH2), 46.20 (CHN), 60.80 (OCH2), 127.89 (CH arom .), 136.73
(C quat. arom .), 156.31 (CO carbam ate), 178.30 (COOH). For C17H23NO4 (305.4) calculated:
66.86% C, 7.59% H, 4.59% N; foun d: 66.65% C, 7.65% H, 4.48% N.
3-[6-(tert-Butoxycarbonamido)-2-methyl-5,6,7,8-tetrahydro-1-naphthyl]propanoic acid (21).
Wh ite solid, yield 94%. 1H NMR (200.130 MHz, CDCl3): 1.42 (s, 9 H, t-Bu); 1.70–1.90 (m ,
1 H, rin g CH2); 198–2.15 (m , 1 H, rin g CH2); 2.29 (s, 3 H, CH3); 2.38–2.50 (m , 2 H, CH2);
2.64 (dd, J = 16.0 an d 7.8, 1 H, rin g CH2); 2.75–3.00 (m , 4 H, rin g CH2 + CH2); 3.07 (dd, J =
16.0 an d 4.8, 1 H, rin g CH2); 3.80–4.05 (m , 1 H, CHN); 4.70 (broad s, 1 H, NH); 6.83 (d, J =
8.0, 1 H arom .); 6.94 (d, J = 8.0, 1 H arom .). For C19H27NO4 (333.4) calculated: 68.44% C,
8.16% H, 4.20% N; foun d: 68.40% C, 8.25% H, 4.17% N.
3-[6-(Benzyloxycarbonamido)-2-methyl-5,6,7,8-tetrahydro-1-naphthyl]propanoic acid (22).
Wh ite solid, yield 95%. 1H NMR (200.130 MHz, CDCl3): 1.72–1.87 (m , 1 H, rin g CH2);
2.01–2.13 (m , 1 H, rin g CH2); 2.28 (s, 3 H, CH3); 2.40–2.49 (m , 2 H, CH2); 2.63 (dd, J = 16.1
an d 7.7, 1 H, rin g CH2); 2.77–2.99 (m , 4 H, rin g CH2 + CH2); 3.07 (dd, J = 16.1 an d 4.9, 1 H,
rin g CH2); 3.90–4.10 (m , 1 H, CHN); 4.79 (broad s, 1 H, NH); 5.09 (s, 2 H, OCH2); 6.83 (d,
J = 8.0, 1 H arom .); 6.94 (d, J = 8.0, 1 H arom .); 7.33 (m , 5 H arom .). For C22H25NO4 (367.4)
calculated: 71.91% C, 6.86% H, 3.81% N; foun d: 72.04% C, 6.91% H, 3.77% N.
The authors thank the European Socrates–Erasmus program for support to C. Alameda Angulo from
the University of Oviedo (Spain), and ORIL Industry company for a loan of functional chromanones.
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