Tripodal molecules derived from ethanoldithiazinanes centered on boron and phosphorus atoms. Structural analyses by NMR and HF/6-31G(d) calculations

Article abstract of DOI:10.1016/j.molstruc.2010.07.019

A series of boric esters, phosphites, phosphates, thiophosphates and selenophosphates derived from 2-(1,3,5-dithiazinan-5-yl)-ethanol (1), 2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanol (2), and 2-(1,3,5-dithiazinan-5-yl)- 1-phenylethanol (3) are reported. Enantiopure compounds (C3 symmetry) were prepared from 2(-) and 3(-) of (R) configuration. The new tripodal molecules were viscous liquids which were mainly characterized by ¹H, ¹³C, ¹¹B, ³¹P, ⁷⁷Se, NMR and VT-NMR experiments. BH₃, BCl₃, pyridine and PPh₃O adducts of boric esters as well as the BH₃ adducts of phosphites were synthesized. The molecular geometries were calculated by HF/6-31G(d). The modeled molecules indicated a preferred ligand conformation which led to the formation of cavities. The complex NMR spectra of isomers were interpreted by comparison with the calculated geometries.

Full text of DOI:10.1016/j.molstruc.2010.07.019

Journal of Molecular Structure 981 (2010) 21–33
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Tripodal molecules derived from ethanoldithiazinanes centered on boron and
phosphorus atoms. Structural analyses by NMR and HF/6-31G(d) calculations
Raúl Colorado-Peralta a, Alfonso Xotlanihua-Flores a, Juan Carlos Gálvez-Ruíz b, Sonia A. Sánchez-Ruíz a,
Rosalinda Contreras a, Angelina Flores-Parra a,
*
a Departamento de Química, Cinvestav México, A.P. 14-740, C.P. 07000, México D.F., Mexico
b Departamento de Ciencias Químico-Biológicas, Universidad de Sonora, Mexico
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 June 2010
Received in revised form 10 July 2010
Accepted 14 July 2010
Available online 22 July 2010
A series of boric esters, phosphites, phosphates, thiophosphates and selenophosphates derived from
2-(1,3,5-dithiazinan-5-yl)-ethanol (1), 2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanol (2), and 2-(1,3,5-
dithiazinan-5-yl)-1-phenylethanol (3) are reported. Enantiopure compounds (C3 symmetry) were
prepared from 2(À) and 3(À) of (R) configuration. The new tripodal molecules were viscous liquids which
were mainly characterized by 1H, 13C, 11B, 31P, 77Se, NMR and VT-NMR experiments. BH3, BCl3, pyridine and
PPh3O adducts of boric esters as well as the BH3 adducts of phosphites were synthesized. The molecular
geometries were calculated by HF/6-31G(d). The modeled molecules indicated a preferred ligand confor-
mation which led to the formation of cavities. The complex NMR spectra of isomers were interpreted by
comparison with the calculated geometries.
Keywords:
Tripodal boric esters
Tripodal phosphites
Tripodal phosphates
Dithiazinanylethanol
C3 compounds
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
pyramidal or tetrahedral), the ligand shape and it substituents affect
the conformation of these molecules.
The reported tripodal molecules are mainly based on aminob-
orates. They are of interest as building blocks for macromolecular
systems such as molecular rotors made with tris(indazolyl)borate
[1]. Tripodal aminoborates are also used as polydentate ligands
for metal ions [2,3]. Enantiopure tripodal ligands are relevant as
enantioselective inductors. The first example of a chiral tris(methi-
mazolyl)borate ligand, has been reported in 2007 [4]. An alkyl-
tris(pyrazolyl)borate bearing a C1 symmetry alkyl group bound
to boron has been used to build octahedral metal centers [5]. A chi-
ral tripodal tris(oxazolinyl)ethane having carbon as the central
atom and a C3 symmetry is a chelating ligand for metal atoms
[6,7]. Some C3 symmetry molecules with phosphorus groups as
substituents and nitrogen as the central atom have found applica-
tion in asymmetric catalysis [8]. Other tripodal compounds where
the central atom is a metal surrounded by phosphorus heterocycles
as substituents are known [9].
The presence of a Lewis acid as the central atom in compounds
bearing amines, makes it interesting to investigate whether, in
spite of the steric demand intramolecular, coordination is possible.
If the compounds are able to present intramolecular N ? B coordi-
nation, then a fluxional behavior is possible by competition be-
tween the three nitrogen atoms for the boron coordination.
The symmetry of the tripodal molecules is very important. The
organization of the branches and the molecular stereochemistry
will depend on the presence of stereogenic centers at C8 which car-
ry methyl or phenyl substituents. C3 symmetry molecules will be
obtained if the three ligands have the same chirality and C1 sym-
metry compounds will be produced if they have different chirality.
The structural analysis of the isomers will be complex, particu-
larly when crystalline structures are not available for X-ray
diffraction analyses, as is the case in the present study where the
compounds are viscous liquids. In this case, modelization is a very
powerful tool for structural analysis, as we will discuss here.
In spite of the importance of tripodal molecules, to our knowl-
edge, there are no examples where the central group is a planar
tricoordinated boric ester, nor phosphites or phosphates. Conse-
quently we decided to prepare tripodal compounds 4–14 using
ethanoldithiazinanes 1–3 (Scheme 1). We were interested in
exploring how the geometry of the central atom (planar, trigonal
2. Experimental
2.1. General
All solvents were freshly distilled before use. Due to the high
reactivity of synthesized compounds, they were isolated pure
directly from the reactions and their structure determined. The
* Corresponding author.
E-mail address: aflores@cinvestav.mx (A. Flores-Parra).
0022-2860/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2010.07.019

22
R. Colorado-Peralta et al. / Journal of Molecular Structure 981 (2010) 21–33
R
R
R
N
7
S
O
S
8
N
S
R
B
O
2
4
6
S
S
N
OH
S
Et3N, PhCH3
BCl -DMS
O
1/3
3
N
1 R = H
2 R = Me
3 R = Ph
- Et3NHCl
4 R = H
5 R = Me
6 R = Ph
S
S
Et3N, PhCH3
PCl3
1/3
- Et3NHCl
R = H, Me,
R
Y
P
R
N
S
R
S
O
R
N
S
O
R
N
S
P
S
S
O
O
N
S
O
R
S
S
N
O
S
N
7 R = H
8 R = Me
S
R= H
9(Y= O), 11(Y= S), 13(Y= Se)
R= Me 10(Y= O), 12(Y= S), 14(Y= Se)
S
Scheme 1. Syntheses of tripodal compounds 4–14.
1H, 13C, 11B, 15N, 31P and 77Se NMR spectra were recorded with a
JEOL GXS-270 (1H 270 MHz) or a JEOL Eclipse (1H 400 MHz). 1H
and 13C, 11B, 15N, 31P and 77Se d (ppm) are referenced to TMS,
BF3ÁOEt2, MeNO2, H3PO4 and SeMe2, respectively. 1H and 13C chem-
ical shifts were unequivocally assigned by 2D experiments HETCOR
and COSY. Elemental analyses were performed on a FLASH(EA)
1112 Series, Thermo Finnigan apparatus. The MS spectra were ob-
tained at 20 eV in a HP 5989 and +TOF high resolution spectra in an
Agilent Technologies LC/MCD instrument.
C6H13NOS2: C, 40.19; H, 7.31; N, 7.81. Found: C, 40.07; H, 7.79;
N, 7.83.
2.4. Tris[2-(1,3,5-dithiazinan-5-yl)-ethanyl]-boric ester (4) general
procedure
Under an anhydrous N2 atmosphere: compound 1 (500 mg,
3.0 mmol) was dissolved in toluene (50 mL) and NEt3 (0.43 mL,
3.0 mmol) was added. The reaction mixture was stirred at rt for
30 min, then it was cooled to À78 °C and a solution of BCl3 in hex-
ane (1 M, 1 mL, 1.0 mmol) was added. The mixture was stirred for
3 h at À78 °C. The reaction was left to warm to room temperature,
then it was filtered and the solvent evaporated. Compound 4 is a
yellow liquid (510 mg, 98%). NMR (d ppm, CDCl3, 25 °C), 1H: 4.34
(br s, 12H, H4, H6), 3.99 (br s, 6H, H2), 3.75 (t, 6H, 3J 5.4 Hz, H8),
3.05 (t, 6H, 3J 5.5 Hz, H7). 13C: 61.2 (C8), 58.9 (C4, C6), 50.3 (C7),
33.9 (C2). 11B: +17.5. 15N: À350.7. NMR (tol-d8, À90 °C), 1H: 4.83
(d, 6H, 2J 12.3, H4ax, H6ax), 4.59 (d, 3H, 2J 12.3, H2ax) 4.07 (d,
6H, 2J 12.3, H4eq, H6eq), 3.79 (br s, 3H, H8a), 3.59 (d, 3H, 2J 12.3,
H2eq), 3.50 (br t, 2H, 3J 5.4 Hz, H8b), 3.09 (br s, 3H, H7a), 3.03
(br t, 3H, 3J 5.4 Hz, H7b). 13C: [60.0, 58.9, C8], 58.0 (C6), 57.9
(C4), [51.4, 49.8, C7], 32.9 (C2). 11B: +9.0. MS, (20 eV) m/z (%):
503(3), 378(9), 247(7), 213(11), 165(12), 155(20), 100(30),
86(52), 42(100). Anal. Calcd. for C15H30BN3O3S6: C, 35.77; H,
6.00; N, 8.34. Found: C, 36.03; H, 5.89; N, 8.53.
2.2. X-ray crystallography
Crystal data for compound 2(À) were obtained with an Enraf–
Nonius Kappa CCD diffractometer equipped with an area detector.
Relevant data are reported in the complementary information.
Computation was performed by SHELXL (Sheldrick 1993) Crystal-
lographic data (excluding structure factors) have been deposited
with the Cambridge Crystallographic Data Bank (CCDC 777208).
Copies of the data can be obtained free of charge on application
to, 12 Union Road, Cambridge CB2 1EZ, UK [Fax: Int. Code +44
(1223) 336 033; E-mail: deposit@ccdc.cam.ac.uk.
2.3. (R)-(À)-2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanol [2(À)]
Compound 2(À) was prepared following the procedure reported
for compounds 1–3 [9]. To (R)-(À)-1-amino-2-propanol (5 g,
2.5. Tris[2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanyl]-boric ester [5( )]
65.2 mmol) in water (50 mL),
a solution of NaSH (11.0 g,
196 mmol) and aq. formaldehyde (37%, 24.3 mL, 326 mmol) was
slowly added at 5 °C. The mixture was stirred for 30 min at 0 °C
and then 24 h at rt. The white solid was filtered and washed with
water (20 mL). The residual solution was extracted with CH2Cl2,
the solution was dried with Na2SO4 and then the solvent evapo-
rated. Compound 2(À) crystallized from CH2Cl2 (8.4 g, 72%). M.p.
70 °C. NMR (d ppm, CDCl3, 25 °C), 1H: 4.37 (br s, 4H, H4, H6),
4.03 (br s, 2H, H2), 3.76 (qdd, 1H, 3J 6.3, 9.9, 3.1 Hz, H8), 3.04
(dd, 1H, 2J 13.5, 3J 3.1 Hz, H7a), 2.59 (s, 1H, OH), 2.43 (dd, 1H, 2J
13.5, 3J 9.9 Hz, H7b), 1.13 (d, 3H, 3J 6.3 Hz, H9). 13C: 63.8 (C8),
58.8 (br s, C4, C6), 57.3 (C7), 33.7 (C2), 20.2 (C9). 15N: À350.9.
Compound 5( ) was prepared following the procedure for com-
pound 4, from 2( ) (500 mg, 2.8 mmol), NEt3 (0.4 mL, 2.8 mmol)
and a solution of BCl3 in hexane (1 M, 0.93 mL, 0.93 mmol). Com-
pound 5( ) is a pale yellow liquid (510 mg, 98%). NMR (d ppm,
CDCl3, 25 °C), 1H: 4.34 (br s, 12H, H4, H6), 4.15 (br ddd, 3H 3J 4.4,
7.3, 6.2 Hz, H8), 4.03 (br s, 6H, H2), [3.05 (dd, 2J 13.6, 3J 5.4 Hz),
3.04 (dd, 2J 13.6, 3J 3.7 Hz), 3.05 (d, 3J 7.3 Hz) 2:1:1 ratio, H7a],
[2.82 (dd, 2J 13.6, 3J 7.5 Hz), 2.76 (dd, 2J 13.6, 3J 7.5 Hz), 2.84 (t, 3J
7.3 Hz)] 2:1:1 ratio, H7b], 1.08 (d, 9H, 3J 6.2 Hz, H9). 13C: [66.5,
66.4, 66.3, 1:2:1 ratio, C8], 59.6 (C4, C6), [56.4, 56.3, 56.2, 1:2:1
ratio, C7], 34.0 (C2), 20.7 (C9). 11B: +17.2. 15N: À350.9. NMR
(tol-d8, À90 °C), 1H: 4.83 (d, 6H, 2J 12.1, H4a and H6a), 4.58
(d, 3H, 2J 12.1, H2a), 4.04 (d, 6H, 2J 12.1, H4e, 2H6e), 3.86 (m, 1H,
H8), 3.61 (d, 3H, 2J 12.1, H2e), 3.02 (m, 3H, H7a), 2.77 (m, 3H,
[a
]
D
À46.49 (CH2Cl2, 25 °C). MS, (20 eV) m/z (%): 179(38),
134(60), 122(37), 100(46), 76(100), 57(65), 42(72); (+)TOF m/z
(amu): (C6H14NOS2)+, 180.0511, calcd. 180.0516. Anal. Calcd. for

R. Colorado-Peralta et al. / Journal of Molecular Structure 981 (2010) 21–33
23
3H7b), 1.09 (br s, 9H, H9). 13C: [66.2, 66.0, 65.9, 1:2:1 ratio, C8],
59.9, 59.6 (C4 or C6), 58.0, 57.7 (C6 or C4), [56.1, 56.0, 55.8, 1:2:1
ratio, C7], 33.4 (C2), 20.1, 20.0 (C9). 11B: +9.1. MS, (20 eV) m/z
(%): 545(21), 420(38), 275(30), 241(36), 183(49), 134(29),
2.9. Tris-{2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanyl}-phosphite
[8( )]
Compound 8( ) was prepared following the procedure for 7,
from 5( ) (500 mg, 2.79 mmol), NEt3 (0.4 mL, 2.8 mmol) and PCl3
(0.08 mL, 0.9 mmol). Compound 8( ) is a pale yellow liquid
(500 mg, 95%). NMR (d ppm, CDCl3, 25 °C), 1H: 4.35 (br s, 12H,
H4, H6), 4.22 (ddd, 3H, 3J 3.1, 7.4, 6.3 Hz, H8), 4.05 (br s, 6H, H2),
3.07 (dd, 3H, 2J 13.0, 3J 3.1 Hz, H7a), 2.93 (dd, 3H, 2J 13.0, 3J
7.4 Hz, H7b), 1.21 (d, 9H, 3J 6.3 Hz, H9). 13C: [67.4 (d, 2J(13C–31P)
11.5 Hz), 67.3 (d, 2J(13C–31P) 11.2 Hz), 67.2 (d, 2J(13C–31P)
11.2 Hz), 67.1 (d, 2J(13C–31P) 11.7 Hz), 1:1:1:1 ratio, C8], 59.1 (C4,
C6), 55.6 (C7), 33.5 (C2), 20.5 (C9). 31P: +142.1 and +142.0, 3:1 ratio
3J(31P–1H) 7.4 Hz. Anal. Calcd. for C18H36N3O3PS6: C, 38.21; H, 6.41;
N, 7.43. Found: C, 38.25; H, 6.39; N, 7.58.
100(100), 58(82), 42(60). Anal. Calcd. for
C18H36BN3O3S6: C,
39.62; H, 6.65; N, 7.70. Found: C, 40.03; H, 6.96; N, 7.22.
2.6. Tris[(R)-(À)-2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanyl]-boric
ester [5(À)]
Compound 5(À) was prepared following the same procedure as
for compound 4, from 2(À) (500 mg, 2.8 mmol), NEt3 (0.4 mL,
2.8 mmol) and BCl3 in hexane (1 M, 0.93 mL, 0.93 mmol). Com-
pound 5(À) is a pale yellow liquid (510 mg, 98%). NMR (d ppm,
CDCl3, 25 °C), 1H: 4.38 (br s, 12H, H4, H6), 4.18 (qdd, 3H, 3J = 4.7,
7.4, 6.1 Hz, H8), 4.06 (br s, 6H, H2), 2.99 (dd, 3H, 2J 13.7, 3J
4.7 Hz, H7a), 2.84 (dd, 3H, 2J 13.7, 3J 7.4 Hz, H7b), 1.09 (d, 9H, 3J
6.1 Hz, H9). 13C: 66.5 (C8), 59.5 (C4, C6), 56.2 (C7), 34.0 (C2),
20.4 (C9). 11B: +17.2. 15N: À351.0. NMR (tol-d8, À50 °C), 1H: 4.52
(d, 3H, 2J 13.3, H4ax or H6ax), 4.45 (d, 3H, 2J 3.3, H6ax or H4ax),
4.26 (qdd, 3H, 3J 4.7, 7.7, 6.1, H8), 4.14 (d, 3H, 2J 13.3, H2ax), 3.79
(br d, 6H, 2J 13.3, H4eq, H6eq), 3.14 (br d, 3H, H2eq), 3.06 (dd,
3H, 2J 13.3, 3J 4.7, H7a), 2.76 (dd, 3H, 2J 13.3, 3J 7.7, H7b), 1.07 (d,
9H, 3J 6.1, H9). 13C: 65.8 (C8), 59.7 (C4 or C6), 58.0 (C6 or C4),
56.0 (C7), 33.5 (C2), 20.6 (C9). 11B: +9.1.3. MS, (20 eV) m/z (%):
545(21), 420(38), 275(30), 241(36), 183(49), 134(29), 100(100),
58(82), 42(60).
2.10. Tris-{(R)-(À)-2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanyl}-
phosphite [8(À)]
Compound 8(À) was prepared following the procedure for 7,
from 5(À) (500 mg, 2.8 mmol) NEt3 (0.4 mL, 2.8 mmol) and PCl3
(0.1 mL, 0.9 mmol). Compound 8(À) is
a pale yellow liquid
(510 mg, 97%). NMR (d ppm, CDCl3, 25 °C), 1H: 4.34 (br s, 12H,
H4, H6), 4.20 (qdd, 3H 3J 6.2, 3.3, 7.6 Hz, H8), 4.02 (br s, 6H, H2),
3.06 (dd, 3H, 2J 13.2, 3J 3.3 Hz, H7a), 2.92 (dd, 3H, 2J 13.2, 3J
7.6 Hz, H7b), 1.19 (d, 9H, 3J 6.2 Hz, H9). 13C: 67.1 (d, 2J(13C–31P)
10.7 Hz, C8), 59.0 (C4, C6), 55.5 (C7), 33.4 (C2), 20.4 (C9). 31P:
+142.0, 3J(31P–1H) 7.4 Hz.
2.7. Tris[2-(1,3,5-dithiazinan-5-yl)-1-phenyl-ethanyl]-boric ester
[6( )]
2.11. Tris-{2-(1,3,5-dithiazinan-5-yl)-ethanyl}-phosphate (9)
Compound 6( ) was prepared following the procedure for com-
pound 4, from 3( ) (500 mg, 2.1 mmol), NEt3 (0.3 mL, 2.1 mmol)
and BCl3 in hexane (1 M, 0.7 mL, 0.7 mmol). Compound 6( ) is a
pale yellow liquid (500 mg, 98%). NMR (d ppm, CDCl3, 25 °C), 1H:
7.40–7.10 (m, 15H, Ph), 5.10 (br dd, 3J 7.5, 4.2 Hz, 3H, H8), 4.28
(br s, 12H, H4, H6), 4.12 (br s, 6H, H2), 3.95 (br dd, 2J 13.5, 3J
4.2 Hz, 3H, H7a), 3.11 (br dd, 2J 13.5, 3J 7.5 Hz, 3H, H7b). 13C:
141.9 (Ci), 128.3 (Co), 127.6 (Cp), 126.1 (Cm), [73.7, 73.6, 73.5,
1:2:1 ratio, C8], 59.6 (br, C4, C6), [57.0, 56.9, 56.8, 1:2:1 ratio,
C7], 33.7 (C2). 11B: +17.8 (s). 15N: À350.4. VT NMR (tol-d8,
À60 °C) 1H 7.40–7.00 (m, 15H, H–Ph), 4.89 (d, 3H, 2J 13.0, H4a or
H6a), 4.83 (d, 3H, 2J 13.0, H6a or H4a), 4.70 (m, 2H, H8), 4.60 (d,
3H, 2J 13.3, H2a), 4.16 (d, 3H, 2J 13.0, H4e or H6e), 4.07 (d, 3H, 2J
13.0, H6e or H4e), 3.60 (d, 3H, 2J 13.3, H2e), 3.22 (m, 3H, H7a),
2.91 (m, 3H, H7b). 13C: 141.9, 141.8 (Ci), 128.1, 127.9 (Cm),
127.0, 126.9 (Cp), 126.0, 125.9 (Co), 73.8, 73.6(br) (C8), 59.8 (br,
C6 or C4), 57.6 (br, C4 or C6), 56.8(br), 56.6 (C7), 33.0 (C2). 11B:
+8.9. Anal. Calcd. for C33H42BN3O3S6Á1/2H2O: C, 53.50; H, 5.85; N,
5.67. Found: C, 53.33; H, 5.55; N, 5.51.
General procedure: To a solution of H2O2 (30%, 80 mL,
1.0 mmol) a solution of compound 7 (500 mg, 1.0 mmol) in CH2Cl2
(30 mL) was added. The mixture was stirred 2 h at rt, and the sol-
vent evaporated. Compound 9 is a colorless viscous liquid (430 mg,
83%). NMR (d ppm, CDCl3, 25 °C), 1H: 4.35 (br s, 12H, H4, H6), 4.12
(br t, 6H, 3J 5.5 Hz, H8), 4.02 (br s, 6H, H2), 3.29 (t, 6H, 3J 5.5 Hz,
H7). 13C: 63.1 (d, 2J(13C–31P) 6.2 Hz, C8), 58.5 (C4, C6), 49.5 (d,
3J(13C–31P) 4.6 Hz, C7), 33.8 (C2). 31P: +9.4.
2.12. Tris-{2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanyl}-phosphate
[10( )]
Compound 10( ) was prepared following the procedure for 9,
from 8( ) (500 mg, 0.9 mmol) and a solution of H2O2 (30%,
70 mL, 0.9 mmol). Compound 10( ) is a colorless viscous liquid
(500 mg, 97%). NMR (d ppm, CDCl3, 25 °C), 1H: 4.32 (qdd, 3H, 3J
5.9, 3.3, 7.3 Hz, H8), 4.27 (br s, 12H, H4, H6), 4.11 (br s, 6H, H2),
3.04 (dd, 3H, 2J 14.2, 3J 3.3 Hz, H7a), 2.81 (dd, 3H, 2J 14.2, 3J
7.3 Hz, H7b), 1.15 (d, 3J 5.9 Hz, H9). 13C: [73.4 (d, 2J(13C–31P)
6.1 Hz), 73.3 (d, 2J(13C–31P) 5.4 Hz), 1:1 ratio, C8], 59.3 (C4, C6),
[55.1 (d, 3J(13C–31P) 6.1 Hz), 55.0 (d, 3J(13C–31P) 5.4 Hz), C7], 33.7
(C2), [19.8 (d, 3J(13C–31P) 2.3 Hz), 19.7 (d, 3J(13C–31P) 2.3 Hz), C9].
31P: À1.60 (3J(31P–1H) 7.45 Hz), À1.65 (3J(31P–1H) 7.45 Hz), 1:3 ra-
tio. Anal. Calcd. for C18H36N3O4PS6Á1/6C7H8: C, 38.55; H, 6.30; N,
7.04. Found: C, 38.25; H, 6.39; N, 6.58.
2.8. Tris-{2-(1,3,5-dithiazinan-5-yl)-ethanyl}-phosphite (7)
General procedure : To a solution of compound 1 (500 mg,
3.0 mmol) in toluene (50 mL) NEt3 (0.43 mL, 3.0 mmol) was added
at À5 °C. The mixture was stirred 30 min at rt, then cooled to
À78 °C and PCl3 (137 mg, 1.0 mmol) dissolved in hexane (10 mL)
was added. The mixture was stirred for 2 h, at À78 °C, then the
reaction was left to warm to room temperature and filtered under
N2 atmosphere and the solvent evaporated. Compound 7 is a yel-
low liquid (500 mg, 95%). NMR (d ppm, CDCl3, 25 °C), 1H: 4.33 (br
s, 12H, H4, H6), 3.99 (br s, 6H, H2), 3.78 (dt, 6H, 3J 5.6 Hz, H8),
3.12 (t, 6H, 3J 5.6 Hz, H7). 13C: 60.1 (d, 2J(31P–13C) 9.9 Hz, C8),
58.8 (C4, C6), 50.0 (d, 3J(13C–31P) 4.6 Hz, C7), 33.9 (C2). 31P:
+140.6, 3J(31P–1H) 7.4 Hz. Anal. Calcd. for C15H30N3O3S6PÁCHCl3:
C, 32.16; H, 5.58; N, 7.50. Found: C, 32.34; H, 5.96; N, 7.85.
2.13. Tris-{(R)-(À)-2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanyl}-
phosphate [10(À)]
Compound 10(À) was prepared following the procedure for 9,
from 8(À) (500 mg, 0.9 mmol) and a solution of H2O2 (30%,
70 mL, 0.9 mmol). Compound 10(À) is colorless viscous liquid
(490 mg, 95%). NMR (d ppm, CDCl3, 25 °C), 1H: 4.38 (qdd, 3H, 3J
4.2, 3.7, 7.3 Hz, H8), 4.30 (br s, 12H, H4, H6), 4.16 (br s, 6H, H2),
3.12 (dd, 3H, 2J 10.2, 3J 3.7 Hz, H7a), 2.89 (dd, 3H, 2J 10.2, 3J

24
R. Colorado-Peralta et al. / Journal of Molecular Structure 981 (2010) 21–33
7.3 Hz, H7b), 1.23 (d, 3J 4.2 Hz, H9). 13C: 73.4 (d, 2J(13C–31P) 5.4 Hz,
C8), 59.4 (C4, C6), 55.0 (d, 3J(13C–31P) 4.6 Hz, C7), 33.8 (C2), 19.8
(C9). 31P: À1.45, 3J(31P–1H) 7.45 Hz.
(br s, 12H, H4, H6), 4.03 (br s, 6H, H2), 3.15 (dd, 3H, 2J 13.3,
3J 3.3 Hz, H7a), 2.94 (dd, 3H, 2J 13.3, 3J 7.3 Hz, H7b), 1.24 (d,
3J 3.3 Hz, H9). 13C: [74.9 (d, 2J(13C–31P) 5.4 Hz), 74.8 (d, 2J(13C–31P)
5.4 Hz), 74.7 (d, 2J(13C–31P) 6.1 Hz), 74.6 (d, 2J(13C–31P) 6.1 Hz),
1:1:1:1 ratio, C8], 59.6 (C4, C6), [54.9 (d, 3J(13C–31P) 3.0 Hz), 54.8
(d, 3J(13C–31P) 3.0 Hz), 1:1 ratio, C7], 33.9 (C2), [19.5 (d,
3J(13C–31P) 2.3 Hz), 19.4 (d, 3J(13C–31P) 2.3 Hz), C9]. 31P: +72.0
(1J(31P–77Se) 934.3 Hz, 3J(31P–1H) 12.4 Hz), +71.2 (1J(31P–77Se)
929.6 Hz, 3J(31P–1H) 12.4 Hz), 3:1 ratio. 77Se: [À351.4 (d,
1J(77Se–31P) 929.6 Hz), À354.8 (d, 1J(77Se–31P) 934.3 Hz), 3:1 ratio].
(+)TOF m/z (amu): (C18H37N3O3PS6Se)+ found 646.0040 Calcd.
646.0056. Anal. Calcd. for C18H36N3O3PS6Se: C, 33.53; H, 5.63; N,
6.52. Found: C, 33.73; H, 6.13; N; 6.97.
2.14. Tris-{2-(1,3,5-dithiazinan-5-yl)-ethanyl}-thiophosphate (11)
Compound 11 was prepared by adding sulfur (100 mg,
3.0 mmol) to a solution of compound 7 (500 mg, 1.0 mmol) in
CH2Cl2 (30 mL). After stirring for 2 h at rt, the solids were removed
by filtration and then the solvent was evaporated. Compound 11 is
a pale yellow liquid (490 mg, 93%). NMR (d ppm, CDCl3, 25 °C), 1H:
4.42 (br s, 12H, H4, H6), 4.13 (dt, 6H, 3J 5.4 Hz, H8), 4.08 (br s,
6H, H2), 3.29 (t, 6H, 3J 5.4 Hz, H7). 13C: 65.8 (d, 2J(13C–31P)
6.1 Hz, C8), 58.8 (C4, C6), 49.1 (d, 3J(13C–31P) 7.7 Hz, C7), 33.9
(C2). 31P: +70.3.
2.19. Tris-{(R)-(À)-2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanyl}-
selenophosphate [14(À)]
2.15. Tris-{2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanyl}-
thiophosphate [12( )]
Compound 14(À) was prepared following the procedure for 11,
from 8(À) (500 mg, 0.9 mmol) and selenium (210 mg, 2.7 mmol).
Compound 14(À) is a pale yellow liquid (560 mg, 98%).
NMR (d ppm, CDCl3, 25 °C), 1H: 4.66 (qdd, 3H, 3J 6.3, 3.2, 7.3 Hz,
H8), 4.41 (br s, 12H, H4, H6), 4.10 (br s, 6H, H2), 3.27 (dd, 3H, 2J
13.4, 3J 3.2 Hz, H7a), 3.01 (dd, 3H, 2J 13.4, 3J 7.3 Hz, H7b), 1.33 (d,
3J 6.3 Hz, H9). 13C: 74.7 (d, 2J(13C–31P) 5.6 Hz, C8), 59.5 (C4, C6),
55.0 (d, 3J(13C–31P) 7.7 Hz, C7), 33.9 (C2), 19.4 (d, 3J(13C–31P)
2.8 Hz, C9). 31P: +72.3 (1J(31P–77Se) 932.5 Hz). 77Se: À358.4, d,
1J(77Se–31P) 932.5 Hz.
Compound 12( ) was prepared following the procedure for 11,
from 8( ) (500 mg, 0.9 mmol) and sulfur (90 mg, 2.7 mmol). Com-
pound 12( ) is a pale yellow liquid (500 mg, 95%). NMR (d ppm,
CDCl3, 25 °C), 1H: 4.56 (qdd, 3H, 3J 5.9, 3.1, 7.4 Hz, H8), 4.36 (br s,
12H, H4, H6), 4.05 (br s, 6H, H2), 3.18 (dd, 3H, 2J 13.2, 3J 3.1 Hz,
H7a), 2.95 (dd, 3H, 2J 13.2, 3J 7.4 Hz, H7b), 1.27 (d, 3J 5.9 Hz, H9).
13C: [74.3 (d, 2J(13C–31P) 6.2 Hz), 74.2 (d, 2J(13C–31P) 6.1 Hz), 74.1
(d, 2J(13C–31P) 6.9 Hz), 74.0 (d 2J(13C–31P) 6.9 Hz), 1:1:1 ratio, C8],
59.6 (C4, C6), [55.0 (d, 3J(13C–31P) 3.1 Hz), 54.9 (d, 3J(13C–31P)
3.1 Hz), 1:1 ratio, C7], 33.9 (C2), [19.6 (d, 3J(13C–31P) 3.1 Hz),
19.5 (d, 3J(13C–31P) 3.1 Hz), C9]. 31P: +68.1 (3J(31P–1H) 9.9 Hz)
and +67.6 (3J(31P–1H) 9.9 Hz), 1:3 ratio. Anal. Calcd. for
2.20. N ? B pyridine adduct of tris-{2-(1,3,5-dithiazinan-5-yl)-
ethanyl}-boric ester (15)
C
18H36N3O3PS7ÁS8: C 25.30, H, 4.25; N, 4.92. Found: C, 25.72; H,
General procedure: To compound 4 (25 mg, 0.5 mmol) in CH2Cl2
(30 mL), pyridine (0.04 mL, 0.5 mmol) was added at rt. The solvent
was evaporated after 10 min and 15 was obtained as a yellow li-
quid, (29 mg, 98%). NMR (d ppm, CDCl3, 25 °C), 1H: 8.17 (d, 2H, 3J
5.9 Hz, H–Pyo), 7.18 (t, 1H, 3J 7.6 Hz, H–Pyp), 6.80 (dd, 2H, 3J 5.9,
7.6 Hz, H–Pym), 4.05 (br s, 12H, H4, H6), 3.68 (br s, 6H, H2), 3.35
(t, 6H, 3J 5.5 Hz, H8), 2.83 (t, 6H, 3J 5.5 Hz, H7). 13C: 149.4 (C–
Pyo), 135.7 (C–Pyp), 123.5 (C–Pym), 58.9 (C8), 58.4 (C4, C6), 51.3
(C7), 33.5 (C2). 11B: +5.5. NMR (CD2Cl2, À60 °C). 1H: 8.41 (br s,
2H, H–Pyo), 7.65 (br s, 1H, H–Pyp), 7.24 (br s, 2H, H–Pym), 4.66
(br s, 12H, H4, H6), 4.39 (br s, 6H, H2), 3.90 (br s, 6H, H8), 2.94
(br s, 6H, H7). 13C: 148.7 (C–Pyo), 137.3 (C–Pyp), 124.4 (C–Pym),
58.7 (C8), 58.5 (C4, C6), 51.1 (C7), 33.8 (C2). 11B: +5.6.
4.45; N, 4.57.
2.16. Tris-{(R)-(À)-2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanyl}-
thiophosphate [12(À)]
Compound 12(À) was prepared following the procedure for 11,
from 8(À) (500 mg, 0.96 mmol) and sulfur (90 mg, 2.7 mmol).
Compound 12(À) is a yellow viscous liquid (500 mg, 95%). NMR
(d ppm, CDCl3, 25 °C), 1H: 4.57 (qdd, 3H, 3J 6.2, 3.0, 7.6 Hz, H8),
4.39 (br s, 12H, H4, H6), 4.11 (br s, 6H, H2), 3.22 (dd, 3H, 2J 13.2,
3J 3.0 Hz, H7a), 2.96 (dd, 3H, 2J 13.2, 3J 7.6 Hz, H7b), 1.26 (d, 3J
6.2 Hz, 9H, H9). 13C: 73.9 (d, 2J(13C–31P) 6.2 Hz, C8), 59.5 (C4, C6),
55.1 (d, 3J(13C–31P) 7.6 Hz, C7), 33.7 (C2), 19.5 (d, 3J(13C–31P)
3.2 Hz, C9). 31P: +68.2, 3J(31P–1H) = 9.9 Hz.
2.21. N ? B pyridine adduct of tris-[2-(1,3,5-dithiazinan-5-yl)-1-
methyl-ethanyl]-boric ester [16( )]
2.17. Tris-{2-(1,3,5-dithiazinan-5-yl)-ethanyl}-selenophosphate (13)
Compound 16( ) was prepared following the general procedure,
from 5( ) (251 mg, 0.46 mmol) and pyridine (0.04 mL, 0.46 mmol).
Adduct 6 is a pale yellow liquid (280 mg, 98%). NMR (d ppm, CDCl3,
25 °C), 1H: 8.13 (d, 2H, 3J 5.4 Hz, H–Pyo), 7.13 (t, 1H, 3J 7.7 Hz, H–
Pyp), 6.75 (dd, 2H, 3J 5.4, 7.7 Hz, H–Pym), 3.99 (br s, 12H, H4, H6),
3.60 (br s, 6H, H2), 3.50 (br s, 3H, H8), 2.83 (br dd, 3H, 2J 13.5 Hz,
3J 3.2 Hz, H7a), 2.33 (br dd, 3H, 2J 13.5, 3J 8.7 Hz, H7b), 0.76 (br d,
9H, 3J 6.2 Hz, H9); 13C 149.4 (C–Pyo), 135.6 (C–Pyp), 123.4 (C–Pym),
64.0 (C8), 58.9 (C4, C6), 56.9 (C7), 33.4 (C2), 20.8 (C9). 11B: +4.2.
NMR (CD2Cl2, À60 °C), 1H: 8.46 (br s, 2H, H–Pyo), 7.67 (br s, 1H,
H–Pyp), 7.27 (br s, 2H, H–Pym), 4.75 (d, 3H, 2J 12.8 Hz, H4ax or
H6ax), 4.65 (d, 3H, 2J 12.8 Hz, H6ax or H4ax), 4.46 (d, 3H,
2J 13.1 Hz, H2ax), 4.10 (br s, 3H, H8), 3.91 (d, 6H, 2J 12.8 Hz, H4e
and H6e), 3.52 (d, 3H, 2J 13.1 Hz, H2eq), 3.16 (br d, 3H,
2J 12.8 Hz, H7a), 2.42 (br t, 3H, 2J 12.8 Hz, H7b), 1.02 (d, 9H,
3J 4.8 Hz, H9). 13C: 148.9 (C–Pyo), 137.3 (C–Pyp), 124.4
(C–Pym), 63.6 (C8), 56.9 (C4, C6), 60.7 (C7), 33.7 (C2), 20.7 (C9).
11B: +4.0.
Compound 13 was prepared following the procedure for 11,
from compound 7 (500 mg, 0.96 mmol) and selenium (230 mg,
2.9 mmol) in CH2Cl2 (30 mL). Compound 13 is a pale yellow liquid
(550 mg, 95%). NMR (d ppm, CDCl3, 25 °C), 1H: 4.39 (br s, 12H, H4,
H6), 4.10 (t, 6H, 3J 5.4 Hz, H8), 4.06 (br s, 6H, H2), 3.25 (t, 6H, 3J
5.4 Hz, H7). 13C: 65.6 (d, 2J(13C–31P) 5.3 Hz, C8), 58.0 (C4, C6),
48.1 (d, 3J(13C–31P) 7.7 Hz, C7), 33.2 (C2). 31P: +74.1 (1J(31P–77Se)
950.4 Hz). 77Se: À365.5 (d, 1J(77Se–31P) 950.4 Hz). (+)TOF m/z
(amu): (C15H31N3O3PS6Se)+ found 603.9569 Calcd. 603.9587.
2.18. Tris-{2-(1,3,5-dithiazinan-5-yl)-1-methyl-ethanyl}-selenophos-
phate [14( )]
Compound 14( ) was prepared following the procedure for 11,
from 8( ) (500 mg, 0.89 mmol) and selenium (210 mg, 2.7 mmol).
Compound 14( ) is a pale yellow liquid (550 mg, 96%). NMR (d
ppm, CDCl3, 25 °C), 1H: 4.58 (td, 3H, 3J 3.3, 7.3, 3.3 Hz, H8), 4.33

R. Colorado-Peralta et al. / Journal of Molecular Structure 981 (2010) 21–33
25
2.22. N ? B pyridine adduct of tris-[(R)-(À)-2-(1,3,5-dithiazinan-5-
yl)-1-methyl-ethanyl}-boric ester [16(À)]
the solution was left to warm to room temperature and the solvent
evaporated. Compound 19 is a yellow liquid (194 mg, 80%). NMR (d
ppm, CDCl3, 25 °C), 1H: 4.3 (br s, 12H, H4, H6), 4.0 (br s, 6H, H2),
3.76 (t, 6H, 3J 6.3 Hz, H8), 3.46 (t, 6H, 3J 6.3 Hz, H7). 13C: 62.8
(C4, C6), 61.4 (C8), 51.0 (C7), 31.0 (C2). 11B: +10.4, +17.5. Anal.
Calcd. for C15H30B4Cl9N3O6S6ÁC7H8: C, 26.90; H, 4.04; N, 5.44.
Found: C, 26.73; H, 4.27; N, 5.44.
Compound 16(À) was prepared following the general proce-
dure, from 5(À) (250 mg, 0.5 mmol) and pyridine (0.04 mL,
0.5 mmol). Adduct 16(À) is a pale yellow liquid (280 mg, 98%).
NMR (d ppm, CD2Cl2, À60 °C), 1H: 8.54 (d, 2H, 3J 4.5 Hz, H–Pyo),
7.18 (s, 1H, H–Pyp), 7.02 (s, 2H, H–Pym), 4.30 (d, 3H, 2J 13.3 Hz,
H6ax or H4ax), 4.22 (d, 3H, 2J 13.3 Hz, H4ax or H6ax), 4.02 (d,
3H, 2J 13.4 Hz, H2ax), 3.84 (br s, 3H, H8), 3.76 (d, 3H, 2J 13.3 Hz,
H6eq or H4eq), 3.61 (d, 3H, 2J 13.3 Hz, H4eq or H6eq), 3.21 (d,
3H, 2J 13.0 Hz, H7a), 3.07 (d, 3H, 2J 13.4 Hz, H2eq), 2.87 (t, 3H, 2J
13.0 Hz, H7b), 1.29 (d, 9H, 3J 5.6 Hz, H9). 13C: 149.9 (C–Pyo),
135.9 (C–Pyp), 123.9 (C–Pym), 64.2 (C8), 59.9 (C6 or C4), 57.6 (C4
or C6), 57.2 (C7), 33.3 (C2), 21.5 (C9). 11B: +4.3.
2.27. Tris-[2-(5-methyl-1,3,5,6-boradithiazinan-5-yl)-ethanyl]-boric
ester (20)
To compound 4 (200 mg, 0.39 mmol) in THF (20 mL) a solution
of BH3ÁTHF (0.6 M, 1.2 mmol, 2.5 mL) was slowly added at À78 °C,
then the solution was left to warm to room temperature and then,
the solvent was evaporated. Compound 20 is a viscous yellow li-
quid (192 mg, 90%). NMR (d ppm, CDCl3, 25 °C), 1H: 4.4 (br s,
12H, H4, H6), 4.2 (br s, 6H, H2), 3.8 (t, 3J 5.9 Hz, 6H, H8), 3.5 (t, 3J
5.9 Hz, 6H, H7), 2.7 (s, 9H, H9). 13C: 63.4 (C4), 62.1 (C8), 58.2
(C7), 48.1 (CH3), 33.8 (C2). 11B: À3.8, +17.0. Anal. Calcd. for
2.23. O ? B PPh3O adduct of tris-[2-(1,3,5-dithiazinan-5-yl)-ethanyl]-
boric ester (17)
General procedure: To compound 4 (25 mg, 0.5 mmol) in CH2Cl2
(30 mL) a solution of PPh3O (140 mg, 0.5 mmol) in CH2Cl2 (30 mL)
was slowly added at rt. The reaction was stirred for 10 min, then
the solvent was evaporated, 17 is a yellow liquid (400 mg, 98%).
NMR (d ppm, CDCl3, 25 °C), 1H: 7.65–7.30 (m, 15H, H–Ph), 4.33
(br s, 12H, H4, H6), 3.97 (br s, 6H, H2), 3.58 (t, 6H, 3J 5.4 Hz, H8),
3.10 (t, 6H, 3J 5.4 Hz, H7); 13C 132.5 (d, J(Ci–P) 103.8 Hz, Ci),
132.1 (d, J(Co–P) 9.4 Hz, Co), 132.0 (Cp), 128.6 (d, J(Cm–P) 11.4 Hz,
Cm), 58.9 (C8), 58.5 (C4, C6), 51.4 (C7), 33.9 (C2). 11B: +1.4. 31P:
+29.9. NMR (tol-d8, À30 °C), 1H: 7.60–7.00 (m, 15H, H–Ph), 4.48
(br s, 12H, H4, H6), 4.17(br s, 6H, H2), 3.80 (s, 6H, H8), 3.08 (s,
6H, H7). 13C: 132.3 (d, J(Ci–P) 103.8 Hz, Ci), 132.2 (d, J(Co–P)
10.0 Hz, Co), 132.2 (Cp), 128.8 (d, J(Cm–P) 12.3 Hz, Cm), 58.8 (C8),
58.4 (C4, C6), 51.2 (C7), 33.6 (C2). 11B: +1.3. 31P: +29.8.
C
33H42BN3O3S6Á3/4C7H8: C, 39.60; H, 7.38; N, 6.84. Found: C,
39.17; H, 7.63; N, 7.10.
2.28. P ? BH3 adduct of tris-{2-(1,3,5-dithiazinan-5-yl)-ethanyl}-
phosphite (21)
To a fresh solution of compound 7 (110 mg, 0.2 mmol) in ben-
zene (20 mL) a solution of BH3ÁDMS (0.6 M, 0.44 mL, 0.2 mmol)
was slowly added at À78 °C. After 5 min the solution was left to
warm to room temperature and the solvent was evaporated. Com-
pound 21 is a pale yellow liquid (100 mg, 98%). NMR (d ppm, CDCl3,
25 °C), 1H: 3.97 (s, 12H, H4, H6), 3.84 (dt, 3J 5.4, 3J(P–H) 7.6 Hz, H8),
3.80 (s, 6H, H2), 3.08 (t, 6H, 3J 5.4 Hz, H7); 13C 64.9 (d, 2J(13C–31P)
3.4 Hz, C8), 59.0 (C4, C6), 51.4 (C7), 33.9 (C2). 31P: +119.4
(2J(31P–13C) 3.4, 3J(31P–1H) 7.6 Hz). Anal. Calcd. for C15H33BN3O3PS6:
C, 33.51; H, 6.36; N, 7.82. Found: C, 33.26; H, 6.45; N, 8.03.
2.24. O ? B PPh3O adduct of tris-[2-(1,3,5-dithiazinan-5-yl)-1-
methyl-ethanyl]-boric ester [18( )]
2.29. P ? BH3 adduct of tris-{2-(5-methyl-1,3,5,6-boradithiazinan-5-
yl)-ethanyl}-phosphite (22)
Compound 18( ) was prepared following the procedure for
compound 17, from 5( ) (250 mg, 0.5 mmol) and PPh3O (130 mg,
0.5 mmol). Adduct 18( ) is a pale yellow liquid (400 mg, 98%).
NMR (d ppm, tol-d8, 0 °C), 1H: 7.60–7.00 (m, 15H, H–Ph), 4.14 (br
s, 12H, H4, H6), 3.79 (br s, 6H, H2), 3.64 (m, 3H, H8), 3.08 (br dd,
3H, 3J 3.4, 2J 13.4 Hz, H7a), 2.52 (br dd, 3H, 3J 8.8, 2J 13.4 Hz,
H7b), 1.00 (br s, 9H, H9); 13C 132.3 (d, J(Ci–P) 101.7 Hz, Ci), 132.1
(d, J(Co–P) 10.0 Hz, Co), 132.0 (Cp), 128.7 (d, J(Cm–P) 11.5 Hz, Cm),
64.0 (C8), 59.9 (C4, C6), 56.9 (C7), 33.6 (C2), 21.1 (C9). 11B: +1.2.
31P: +29.9.
To a fresh solution of 7 (210 mg, 0.4 mmol) in toluene (20 mL) a
solution of BH3ÁDMS (0.6 M, 1.8 mL, 0.84 mmol) was slowly added
at À78 °C. After 5 min the solution was left to warm to room temper-
ature and the solvent was evaporated. Compound 22 is a pale yellow
liquid (208 mg, 97%). NMR (d ppm, CDCl3, 25 °C), 1H: 4.40 (s, 6H, H6),
4.20 (s, 6H, H2), 3.80 (br t, 3J 5.6 Hz, 6H, H8), 3.50 (t, 3J 5.4 Hz, 6H, H7),
2.70 (s, 9H, H9). 13C: 64.2 (C6), 60.2 (C8), 50.0 (C7), 49.1 (C9), 33.3
(C2). 31P: +118.7. 11B: À3.2 (br s), À44.2 (J(11B–1H) 98.5, J(31P–11B)
90.5 Hz). Anal. Calcd. for C15H42B4N3O3PS6Á4/5C7H8: C, 37.90; H,
7.47; N; 6.44. Found: C, 37.79; H, 8.08; N, 6.22.
2.25. O ? B PPh3O adduct of tris-[(R)-(À)-2-(1,3,5-dithiazinan-5-yl)-
1-methyl-ethanyl]-boric ester [18(À)]
Compound 18(À) was prepared following the procedure for 17,
from 5(À) (250 mg, 0.5 mmol) and PPh3O (130 g, 0.5 mmol). Adduct
18(À) is a pale yellow liquid (395 mg, 98%). NMR (d ppm, tol-d8,
0 °C), 1H: 7.60–7.10 (m, 15H, H–Ph), 4.37 (br s, 12H, H4, H6), 4.01
(br s, 6H, H2), 3.77 (dd, 3H, 3J 3.6, 6.3, 9.0 Hz, H8), 3.24 (dd, 3H, 3J
3.6, 2J 13.5 Hz, H7a), 2.62 (dd, 3H, 3J 9.0, 2J 13.5 Hz, H7b), 1.12 (d,
9H, 3J 6.3, H9). 13C: 132.6 (d, J(Ci–P) 102.3 Hz, Ci), 132.1 (d, J(Co–P)
10.0 Hz, Co), 132.0 (Cp), 128.7 (d, J(Cm–P) = 12.3 Hz, Cm), 64.0 (C8),
59.0 (C4, C6), 57.2 (C7), 33.8 (C2), 21.1 (C9). 11B: +2.2. 31P: +29.3.
3. Results and discussion
The ethanoldithiazinanes 1–3 were obtained by condensation
of the corresponding ethanolamine with formaldehyde and NaSH
in water (Scheme 2) [10]. Ethanoldithiazinanes 2 and 3 with a C8
substituent were prepared as racemic mixtures and also as an
enantiopure compound 2(À) using the ethanolamines of (R)
configuration.
A crystal of the enantiopure compound 2(À) was analyzed by
X-ray diffraction (Fig. 1). The ring has a chair conformation with
the nitrogen substituent in an axial position. The ethanol group
forms a strong intramolecular O–HÁÁÁN hydrogen bond (2.108 Å).
The N5 and O10 are in an alternated syn conformation [dihedral
angle N5–C7–C8–O10 is 46.1(1)°]. The nitrogen atom is pyramidal
2.26. Tris[2-(5-trichloroborane-1,3,5-dithiazinan-5-yl)-ethanyl]-boric
ester (19)
To a solution of compound 4 (200 mg, 0.4 mmol) in toluene
(30 mL), BCl3ÁDMS (0.16 mL, 1.2 mmol) was added at À5 °C, then
C4–N5–C7 114.4(3)°, C6–N5–C7 115.5(2)°, C4–N5–C6 113.0(2)° [
R

26
R. Colorado-Peralta et al. / Journal of Molecular Structure 981 (2010) 21–33
R
OH
R
OH
S
H2O
S
+
+ 5
H2C=O
NaHS
3
N
NH2
1 R = H
2 R = Me
3 R = Ph
Scheme 2. Synthesis of ethanoldithiazinanes 1–3.
Fig. 2. Superposition of the structure of compound 2 obtained by X-ray diffraction
analyses (black), with its modeled structure (gray).
phites 7 and 8 were oxidized with oxygenated water, sulfur or
selenium, in CH2Cl2, to give the phosphates 9, 10( ), 10(À), 11,
12( ), 12(À), 13, 14( ) and 14(À) which are also viscous liquids
but stable in air (Scheme 1). The formation of boric esters 4–6
was confirmed by 11B NMR spectra (CDCl3, 25 °C), which shows
characteristic broad signals at ꢀ+17 ppm. These data also demon-
strate that at room temperature there is no intramolecular N ? B
coordination (expected N ? boric esters would have a chemical
shift in the range of +5–10 ppm) [17]. The 31P NMR (CDCl3, 25 °C)
spectra of the phosphorus compounds showed characteristic sig-
nals for phosphites 7 and 8 (between +140 and +142 ppm), phos-
phates 9 and 10 (between À2 and +9 ppm), thiophosphates 11
and 12 (between +67 and +68 ppm) and selenophosphates 13
and 14 (between +71 and +72 ppm).
Fig. 1. ORTEP representation of compound 2(À).
angles = 342.9°] and its geometry corresponds to 54% sp3 hybrid-
ization. The angles at the sulfur atoms [C2–S1–C6 97.5(1)° and
C2–S3–C4 96.6(1)°] indicate 36% sp3 hybridization.
The ethanoldithiazinanes 1–3 have been used to synthesize a
series of tris[2-(1,3,5-dithiazinan-5-yl)-ethanyl]-boric esters (4–6),
tris[2-(1,3,5-dithiazinan-5-yl)-ethanyl]-phosphites (7 and 8),
tris[2-(1,3,5-dithiazinan-5-yl)-ethanyl]-phosphates (9 and 10),
tris[2-(1,3,5-dithiazinan-5-yl)-ethanyl]-thiophosphates (11 and
12) and tris[2-(1,3,5-dithiazinan-5-yl)-ethanyl]-selenophosphates
(13 and 14) (Scheme 1). The ligand 1 will give only symmetric tripo-
dal compounds. Racemic ligands 2( ) and 3( ) will produce a mix-
ture of isomers (RRR; SSS; RRS and SSR), whereas the enantiopure
ligand 2(R) will give only one isomer (RRR) of C3 symmetry.
Compounds 4–14 are tripodal molecules with three bulky
dithiazinane groups bound to boron or phosphorous atoms by an
ethanolic chain. The dithiazinanyl heterocycles are quite interest-
ing due to their richness in lone pairs and high reactivity. The con-
figuration of the stereogenic center determines the conformation
of the ligands in the tripodal molecules as we will discuss.
Compounds 4–14 are viscous liquids which could not be ana-
lyzed by X-ray diffraction studies. They were mainly characterized
by 1H, 13C, 11B, 31P, 77Se, and variable temperature NMR experi-
ments, while the structure optimization has been performed by
HF/6-31G(d) calculations. In order to establish the capability of
the tripodal molecules to coordinate, a variety of bases and acids
were added. The coordinating ability of free dithiazinanes has been
tested before, using BX3 reagents (X = H, F or Cl). In all cases the
nitrogen atom is the preferred basic site [11–15]. It is also known
that the free ethanoldithiazinanes are convenient ligands for alu-
minum organometallic compounds [16].
3.2. HF/6-31G(d) calculations
An important aim in our investigation was the structural anal-
ysis of the different tripodal molecules and the evaluation of how
the different substituents and chirality affected the overall molec-
ular conformation. Therefore calculations were performed in order
to obtain the molecular geometries using the Gaussian 98 package
[18]. Geometries were checked to be the minimal by means of the
frequency analysis. Validation of the calculations result from the
NMR analyses and also from the reasonable superposition of the
structure of compound 2 obtained by X-ray diffraction analyses
(black), with its modeled structure (gray), (Fig. 2).
3.2.1. Tripodal borates
A discussion of the main results of the modeled molecules fol-
lows. In all pictorial representations, the hydrogen atoms have
been omitted for better appreciation of the structures. The calcu-
lated geometry of all boric esters is trigonal planar [angles close
to 120°,
R angles = 359.98°] with the oxygen and C8 carbon atoms
lying in the same plane. Two optimized conformations very close
in energy were found for compound 4, Fig. 3. In one of them (a)
three dithiazinanes are oriented towards one face of the molecule.
Distances between nitrogen atoms [N1–N2 6.51 Å, N2–N3 4.89 Å
and N1–N3 4.48 Å] indicate that a cavity has been formed between
the ligands. This arrangement is also promoted by the oxygen
nitrogen syn conformation of the fragment O–CH2–CH2–N. The
second one (b) has two arms oriented towards one face and the
third in the opposite face and is slightly higher in energy than con-
former a (0.4324 kJ/mol). In both conformers hydrogen bonds C–
HÁÁÁO stabilized the structure.
3.1. Synthesis of the tripodal molecules
Compounds 1, 2( ), 2(À), and 3( ) reacted with BCl3-DMS in tol-
uene in presence of NEt3 (20 min, at À78 °C) to give boric esters 4–
6 (Scheme 1). The reaction of 1, 2( ) and 2(À) with PCl3 and NEt3
affords the phosphites 7, 8( ) and 8(À). Compounds 4–8 are vis-
cous yellow liquids, stable only under inert atmosphere. Phos-
In Fig. 4, the (RRR) isomer of compound 6 is shown. The boron,
oxygen and C8 atoms are lying in a helicoidal arrangement, as a
consequence of the three hydrogen bonds between the oxygen

R. Colorado-Peralta et al. / Journal of Molecular Structure 981 (2010) 21–33
27
Fig. 3. Two preferred conformers were found for compound 4. Conformer a has less energy (0.4324 kJ/mol) than conformer b.
a helicoidal arrangement. The distances between the nitrogen
atoms are N1–N2 6.187 Å, N2–N3 5.131 Å and N1–N3 5.066 Å
and it is clear that there is more space for coordination on the face
presenting the methyl groups than on the other face of the mole-
cule (Fig. 6).
It is noteworthy that the calculated model for the 5(SSR) isomer
presented a completely different conformation (Fig. 7). One of the
branches with (S) configuration is located alone on one of the faces.
The opposite face has two enantiomeric branches (S) and (R). The
different arrangement of the isomeric ligands has consequences
in their spectral properties. In the preferred conformation of com-
pound 5(RRR), the three substituents are magnetically equivalent,
and will give only one set of signals for all branches under NMR
analyses. However, the lack of symmetry in diasteromer 5(SSR)
will make each substituent distinct.
3.2.2. Tripodal phosphites
Calculations showed that the geometry of the phosphorus atom
in the modeled phosphites is trigonal pyramidal [P angles are O1–
P–O2 96.53°, O2–P–O3 98.57° and O1–P–O3 103.37°]. The pre-
ferred conformation of compound 7 is described in Fig. 8. The
nitrogen lone pairs are pointing in away from each other. The dis-
tances between them are bigger than in the boric esters [N1–N2
7.896 Å, N2–N3 7.737 Å, N1–N3 4.503 Å].
Fig. 4. View of the optimized geometry for 6(RRR).
For compound 8( ), which bears a methyl group at C8, isomers
8(RRR) and 8(SSR) were analyzed (Fig. 9). In isomer 8(RRR), the
methyl groups are situated on the same face of the plane formed
by the oxygen atoms, whereas the dithiazinanyl groups are on
the opposite face. The C8–H protons are oriented towards the oxy-
gen atoms with distances 2.76, 2.79, 3.0 Å. The molecule has C3
symmetry. A helicoidal arrangement around the phosphorus is also
observed. The distances between the nitrogen atoms in 8(RRR) and
8(SSR) highlight the differing ligand arrangements between the
two diasteromers [8(RRR) N1–N2 5.255, N2–N3 6.693, and N1–
N3 5.210 Å; 8(SSR) N1–N2 5.389, N2–N3 5.173, and N1–N3
6.393 Å]. In isomer (SSR), the heterocycles are on the same face
of the phosphate, however, the branch (R) is arranged perpendicu-
larly to the other two of (S) configuration. It is clear that for isomer
8(SSR), as in the boric ester 5(SSR), asymmetry will lead to three
sets of 1H and 13C NMR signals.
atoms and the C8–H protons. The phenyl groups and ethanoldi-
thiazinanes are also helicoidally oriented. The C4–H protons are di-
rected towards the nitrogen atoms assisting the organization of the
dithiazinanyl groups. The molecule is dissymmetric (C3 symme-
try). The three phenyl groups are oriented towards one boron face,
whereas the dithiazinanyl groups are located on the other face. All
distances between the phenyl centroids are around 6.24 Å, and all
N–N distances are 5.25 Å. This arrangement leads to the formation
of two different cavities. The one formed by the dithiazinanyl
groups is small (0.9 Å is the distance between the axial C4–H
Fig. 5a), whereas the second cavity formed by the phenyl groups
has more space for the possible coordination of a small molecule
(Fig. 5b).
For the isomeric mixture of compound 5, prepared from race-
mic ethanoldithiazinanes 2( ), two diasteromers, (RRR) and
(SSR), were analyzed. For isomer 5(RRR), the three methyl groups
are oriented towards one face, and the three dithiazinanes are lo-
cated on the other face affording two cavities. The boron, oxygen
and C8 atoms form as in the previous analyzed molecule 6(RRR),
3.2.3. Tripodal phosphates
All phosphates (9–14) show the distorted tetrahedral geometry
of phosphorus. Compounds 9 (P@O), 11 (P@S) and 13 (P@Se) all

28
R. Colorado-Peralta et al. / Journal of Molecular Structure 981 (2010) 21–33
Fig. 5. Spacefill representation of compound 6(RRR) showing two views along an axis perpendicular to the boron plane: (a) the face with ethanodithiazinanes and (b) the face
with phenyl groups.
Fig. 6. (a) Distances between C–H protons and oxygen or nitrogen atoms are shown for compound 5(RRR). (b) Spacefill representation of 5(RRR), view of the face with methyl
groups.
Fig. 7. Modeled conformers of 5 (a) isomer (RRR) and (b) isomer (SSR).
have O–P–O bond angles between 102.1 and 103.3°. Angles O–P@X
vary in the range 114.8–116.5°. The P@Y bond lengths are charac-
teristic [13 (P@Se) 2.069 Å, 11 (P@S) 1.925 Å and in 9 (P@O)
1.447 Å]. As compounds 9, 11 and 13 have a similar geometry, only
compound 9 is shown (Fig. 10). Isomers (RRR) and (RRS) of com-
pounds 10, 12 and 14 show similar arrangements to the corre-
sponding phosphites, with analogous stereochemical results
(Fig. 11). The dithiazinane groups produce a bigger cavity in these
phosphates as can be deduced from nitrogen atom distances
[14(À) N1–N2 7.136 Å, N2–N3 4.996 Å, N1–N3 5.089 Å; 12(À)

R. Colorado-Peralta et al. / Journal of Molecular Structure 981 (2010) 21–33
29
Fig. 8. Optimization of the preferred conformer of compound 7.
Fig. 9. Preferred conformers for isomers 8(RRR) (a) and 8(SSR) (b). P angles of 8(RRR) are in the range of 97.96–98.19° and those of 8(SSR) between 96.87° and 99.65°.
C–C–H8 and H7b–C–C–H8 dihedral angles, from the H7a–H8 and
H7b–H8 coupling constants obtained from 1H NMR spectra using
the Karplus equation [19]. The dihedral angles showed that the
ethanolamine group in all compounds adopts a similar preferred
conformation, with nitrogen (N5) and oxygen (O9) in a syn confor-
mation, also found in the solid state for compound 2(À) [N5–C7–
C8–O9 torsional angle is 46.1(1)°]. In the calculated structures 4–
14, the averaged values for the N5–C7–C8–O9 torsional angles vary
from 55.7° to 67.8°. In Table 1, the coupling constants are shown
for compounds 2(À) and 5(À) as well as their calculated angles.
Fig. 10. Optimized geometry for compound 9.
3.4. NMR and the stereochemistry
N1–N2 7.021 Å, N2–N3 4.926 Å, N1–N3 5.026 Å and 10(À) N1–N2
3.4.1. Stereochemical effect on central atoms
5.125 Å, N2–N3 5.189 Å, N1–N3 7.055 Å].
From calculations, it was clear that the tripodal compounds
with ligands without substitution at C8 or having the same config-
uration at C8 would give only one isomer. However, the products
of racemic ethanoldithiazinane would give a mixture of isomers
RRR:RRS:SSR:SSS in a 1:3:3:1 ratio, though the RRR/SSS pairs are
indistinguishable through NMR analysis as is also the case for the
3.3. Ethanolamine fragment conformation analyses by NMR
In order to establish the preferred conformation of the ethanol-
amine fragment in compounds 4–14, we have calculated the H7a–
Fig. 11. Preferred conformers of isomers 10(RRR) and 10(RRS).

30
R. Colorado-Peralta et al. / Journal of Molecular Structure 981 (2010) 21–33
Table 1
RRS/SSR pair. For this reason, NMR analysis of the reaction prod-
ucts of racemic ethanoldithiazinanes gives two signals in a 3:1 ra-
tio. The 31P NMR (CDCl3, 25 °C) spectrum of phosphite 7 and the
enantiopure compound 8(RRR) showed as expected, only one 31P
signal [d31P +140.6, 7 and +142.0, 8(À)] [20]. On the other hand,
the isomers of phosphites 8( ) synthesized from the racemic mix-
ture 2( ), showed two signals at +142.1 [8(SSR)–8(RRS)] and
+142.0 [8(RRR)–8(SSS)] in the expected 3:1 ratio. Their assignment
was checked by adding pure compound 8(À) to the mixture 8( )
and recording the spectrum again, with the corresponding growth
of the signal for 8(RRR) and 8(SSS). The phosphates show a similar
spectral behavior to the phosphites. The 31P NMR spectrum of
phosphates, 10( ) (P@O), 12( ) (P@S) or 14( ) (P@Se), obtained
from the racemic compound 2( ) shows signals in the ratio 3:1.
Spectra for compounds 14 are shown as an example. The 31P and
1H NMR (CDCl3, 25 °C) data [d, ppm] for 2 and 5. Newman projection shows the
preferred conformation for the ethanolamine fragment (configuration R at C8), and
values of the
a
and b dihedral angles, calculated from coupling constants 3J(H–H)
H7b
O
Me
β
N
7a
H
H
8
α
C8 R configuration
.
Cpd
H7a
a
H7b
b
H8
77Se (CDCl3, 25 °C) spectra for 14(RRR) shows
a
31P single
2(À) 3.04 (dd) 3J 3.1 48 2.43 (dd) 3J 9.9 148 3.76 (qdd) 3J 9.9, 3.1
5(À) 2.99 (dd) 3J 4.7 36 2.84 (dd) 3J 7.4 131 4.18 (qdd) 3J 7.4, 4.7
resonance coupled with 77Se [d31P (ppm) +72.3; 1J(31P–77Se)
CH3
H C
Se
P
3
N
S
O
N
S
O
H 3C
S
S
O
N
14(-)
S
S
Fig. 12. d31P and 77Se NMR spectra for compound 14(RRR).
CH
H3 C
3Se
P
N
S
O
N
S
O
H3 C
S
S
O
N
+
14( )
S
-
S
Fig. 13. d31P and 77Se NMR spectra for the isomeric mixture 14( ).

R. Colorado-Peralta et al. / Journal of Molecular Structure 981 (2010) 21–33
31
Table 2
(Table 2). A similar stereochemical result was found for compound
6( ). The same analysis was done with the 1H (CDCl3, 25 °C) NMR
spectra.
Chemical shift data [d, ppm] 13C NMR (CDCl3, 25 °C) of C7 and C8 in compounds 2(À),
5( ) and 5(À).
In the 13C NMR (CDCl3, 25 °C) spectra of isomers 8( ), the C8 sig-
nal presents four doublets due to 2J(31P–13C) coupling one for RRR–
SSS, and the other three for RSS–SRR (Fig. 14).
Cpd
C7
C8
2(À)
5(À)
5( )
57.2
63.6
56.2
66.5
56.4, 56.3, 56.2 [1:2:1] ratio
66.5, 66.4, 66.3 [1:2:1] ratio
3.5. NMR variable temperature experiments
932.5 Hz]. The 77Se spectrum has a doublet at d77Se À358.4
[1J(77Se–31P) 932.5 Hz] (Fig. 12). Spectra of the isomeric mixture
14( ) are in Fig. 13. Signals were assigned by comparison with pure
enantiomer 14(À).
11B NMR experiments at low temperature in toluene-d8 and
THF-d8 showed that the 11B signals of boric esters 4–6 are shifted
from ꢀ+18 ppm (+20 °C) to ꢀ+9 ppm (À90°) which corresponds
to boron coordination by a nitrogen atom (Scheme 3). The 1H
and 13C spectra do not show two different ligands, indicating that
the substituents exhibit a fluxional behavior, exchanging the coor-
dination bond between them [21,22].
From the VT-NMR experiments, the activation energy for the
breaking of the N ? B bond was calculated as 37.8 kJ molÀ1 for
compound 4 and 37.9 kJ molÀ1 for compound 5(RRR). The low va-
lue observed is typical for a weak coordination bond. They are in
the range of similar molecules (30–60 kJ molÀ1 [23–25]). The weak
coordination is attributed to steric effects, and to the nature of the
nitrogen geometry, which is in between tetrahedral and planar,
due to the ring tension, as along with the weak Lewis acid nature
3.4.2. Stereochemical effects on ligands
13C NMR spectra of compound 5( ) synthesized from racemic
ethanolamines showed three signals for C7 and three for C8 in
1:2:1 ratio. One signal corresponds to the pair of isomers 5(RRR)
and 5(SSS) as was equal to that observed in the spectrum of pure
5(RRR). The other two signals in a 1:2 ratio belong to 5(RRS)–
5(SSR). The unequivocal assignment of the 13C spectra was per-
formed by adding to the isomeric mixture of 5, the enantiomeri-
cally pure isomer 5(RRR), which led to an increased signal for
5(RRR)-5(SSS) allowing the identification of the pairs of isomers
Me
Me
N
P
S
O
N
S
O
Me
9
S
S
O
8
7
N
4
6
S
S
2
C8
Fig. 14. 13C NMR spectrum of the isomeric mixture: 8(RRR)–8(SSS) and 8(RRS)–8(SSR). Amplification of C8 signals is shown.
S
S
R
R
O
N
B
N
S
S
O
R
R
N
S
R
B
S
S
O
O
O
R
N
O
N
S
S
4
5
6
R = H
R = Me
R = Ph
N
S
S
S
Scheme 3. N ? B intramolecular coordination of boric esters 4–6.

32
R. Colorado-Peralta et al. / Journal of Molecular Structure 981 (2010) 21–33
B
..
R
R
R
O
R
O
N
N
S
S
O
9
B
S
O
N
S
R
B
R
N
S
B
S
S
S
S
O
8
7
O
N
N
4
15
16
R = H, B: = Py
R = Me, B: = Py
4
5
R = H
R = Me
6
S
S
S
2
R = H, B: = Ph3PO
R = Me, B: = Ph3PO
17
18
Scheme 4. Pyridine and PPh3O adducts of boric esters 4 and 5.
CH3
S
CH3
S
N
O
S
B
O
N
S
.
N
S
3 BH3 THF
BH2
S
O
B
N
S
B
O
O
H2
-78oC, THF
S
H3C
S
O
N
N
BH2
20
S
4
S
S
.
3 BCl3 SMe2
-78oC, C7H8
BCl3
N
BCl3
N
S
O
S
S
B
O
S
O
Cl3B
N
19
S
S
Scheme 5. Reactions of boric ester 4 with boron reagents.
BH3
N
S
P
S
N
O
1 BH3-SMe2
P
N
S
S
O
O
N
S
S
O
S
S
O
S
O
N
N
7
21 (98%)
S
S
S
4 BH3-SMe2
BH3
H3C
N
P
O
CH3
O
N
S
BH2
S
B
S
H2
S
O
N
BH2
S
H3C
S
22 (97%)
Scheme 6. Borane adducts of compound 7.
of the borate. The presence of alkyl or aryl groups in the chains
diminishes the bond strength due to steric effects.
3.6. Lewis base addition to the boric esters
From the VT 1H and 13C NMR experiments in THF-d8 and tolu-
ene-d8, the ring inversion energy was measured as 47.4 kJ molÀ1
for 4, 49.1 kJ molÀ1 for 5 and 48.4 kJ molÀ1 for 6. The presence of
an alkyl or aryl group in the chain increases the energy by 1.7
and 1.0 kJ molÀ1, respectively.
We were interested in establishing whether the ligands sur-
rounding the boron atom were sufficiently bulky to prevent the
coordination of bases. Accordingly, we added a variety of bases
to the boric esters and evaluated the reaction by 11B NMR. Benzyl-
amine, a-methylbenzylamine and pyridine were added to the boric

R. Colorado-Peralta et al. / Journal of Molecular Structure 981 (2010) 21–33
33
esters 4 and 5 and the 11B spectrum recorded (Scheme 4). The
experiments did not show any coordination of benzylamine nor
NMR. 1H, 13C, 31P and 77Se spectra allowed the diasteromer and
conformer assignments. The boric esters presented a fluxional
N ? B coordination as was observed by 11B NMR at low tempera-
ture. The preferred conformations in the tripodal molecules led
to the formation of cavities which left in some of them enough
space for coordination of molecules of low steric demand.
of a-methylbenzylamine even at low temperature. In contrast, pyr-
idine, adducts were observed (11B d +5.6 ppm for 15 and +4.0 for
16). The difference in the coordinating behavior of these amines
is attributed to the lesser volume of the pyridine.
Addition of PPh3 to the boric esters did not show any P ? B
coordination. However, PPh3O which is a less hindered base with
a greater affinity for boron, was coordinated (Scheme 4). The spec-
trum of the boric esters 4 or 5 and ten equivalents of (Ph)3PO at
room temperature showed the coordinated species Ph3PO ? B 17
(d11B +1.3 ppm, d31P +29.8 ppm) and 18 (d11B +1.2 ppm, d31P
+29.5 ppm). These results indicate that these esters are capable
of small bases ligands are useful for small bases coordination.
Acknowledgments
Thanks to Cinvestav for financial support and Conacyt for schol-
arship of R.C.-P. We acknowledge Q. Victor González Díaz for tech-
nical support and J Guthrie and A. Paz-Sandoval for helpful
discussions.
References
3.7. Reactions of boric ester 4 with BCl3 and BH3
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B. Piatek, R.K. Rodebaugh, Inorg. Chem. 42 (2003) 5097.
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Flores-Parra, Heterocycles 63 (2004) 2269.
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In order to establish whether the amine groups of the boric esters
are free enough to coordinate a Lewis acid, three equivalents of
BCl3ÁSMe2 were added to the boric ester 4 and compound 19 was ob-
tained in quantitative yield. Its 11B NMR spectrum showed two sig-
nals in 1:3 ratio, one at +17.5 for B(OR)3, and another at +10.4 for the
N ? BCl3 group. All three nitrogen atoms were coordinated, and the
rings were found to be in conformational equilibrium (Scheme 5).
The reaction of three equivalents of BH3ÁTHF with boric ester 4 at
À78 °C gave compound 20 by a reductive ring opening and rear-
rangement (Scheme 5). The endocyclic BH2 group give a broad band
in the 11B spectrum (d À3.8 ppm) together with the resonance for
the boric atom at +17.0 ppm, in a 3:1 ratio. The 13C NMR spectrum
of 20 has a signal for an N–CH3 group at 48.1 ppm and C4 is shifted
from 58.8 to 63.4 ppm. The structure was established by compari-
son with the reported data for 5-methyl-5-borane-dithiazinane
and 5-methyl-6,1,3,5-boradithiazinane [11,12,15].
[12] G. Cadenas-Pliego, M.-J. Rosales-Hoz, R. Contreras, A. Flores-Parra, Tetrahedron
Asymm. 5 (1994) 633.
[13] A. Flores-Parra, S. Sánchez-Ruiz, C. Guadarrama-Pérez, Eur. J. Inorg. Chem.
(1999) 2063.
[14] J.C. Gálvez-Ruiz, C. Guadarrama-Pérez, H. Nöth, A. Flores-Parra, Eur. J. Inorg.
Chem. (2004) 601.
[15] A. Flores-Parra, S.A. Sánchez-Ruiz, C. Guadarrama-Pérez, H. Nöth, R. Contreras,
Eur. J. Inorg. Chem. 11 (1999) 2069.
[16] J.C. Gálvez-Ruiz, H. Nöth, A. Flores-Parra, Inorg. Chem. 42 (2003) 7569.
[17] T. Mancilla, F. Santiesteban, R. Contreras, A. Klaebe, Tetrahedron Lett. 23
(1982) 1561.
3.8. Reactions of phosphites with BH3
The equimolar reaction of phosphite 7 with BH3–SMe2 gave the
P ? BH3 adduct 21 as the only product, demonstrating that the
phosphorus has enough space for coordination. In an excess of bor-
ane (four equivalents) the borata heterocycles 22 are obtained
(Scheme 6).
[18] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
V.G. Zakrzewski, J.A. Montgomery Jr., R.E. Stratmann, J.C. Burant, S. Dapprich,
J.M. Millam, A.D. Daniels, K.N. Kudin, M.C. Strain, O. Farkas, J. Tomasi, V.
Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli, C. Adamo, S. Clifford, J.
Ochterski, G.A. Petersson, P.Y. Ayala, Q. Cui, K. Morokuma, D.K. Malick, A.D.
Rabuck, K. Raghavachari, J.B. Foresman, J. Cioslowski, J.V. Ortiz, A.G. Baboul,
B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R.L.
Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, C.
Gonzalez, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, J.L.
Andres, C. Gonzalez, M. Head-Gordon, E.S. Replogle, J.A. Pople, Gaussian 98,
Revision A.7, Gaussian, Inc., Pittsburgh, PA, 1998.
[19] C.A.G. Haasnoot, F.A.A.M. DeLeeuw, C. Altona, Tetrahedron 36 (1980) 2783.
[20] J.C. Tebby, Handbook of Phosphorus-31 Nuclear Magnetic Resonance Data,
first ed, CRC Press, Inc., Boca Raton, FL, 1990.
[21] H. Nöth, B. Wrackmeyer, Nuclear Magnetic Resonance Spectroscopy of Boron
Compounds, Springer-Verlag, Berlin Heidelberg New York, Germany, 1978.
[22] B. Wrackmeyer, Ann. Rep. NMR Spectrosc. 20 (1988) 61.
[23] A.L. Gille, T.M. Gilbert, J. Chem. Theory Comput. 4 (2008) 1681.
[24] T.M. Gilbert, J. Phys. Chem. A 108 (2004) 2550.
4. Conclusions
A series of tripodal boric esters (4–6), phosphites (7 and 8),
phosphates (9 and 10), thiophosphates (11 and 12) and seleno-
phosphates (13 and 14) were synthesized. C3 symmetry enantio-
pure compounds were obtained, which may have application in
asymmetric synthesis or a building blocks in material sciences.
The effect of the bulky ethanoldithiazinanes on their structure
was analyzed. The chirality at C8 affected the preferred conforma-
tion of the tripodal compounds. Calculations were very useful for
structural analyses of the compounds. Modeled molecules indi-
cated the preferred conformations and how they depend on the
size and chirality of substituents. Analyses were confirmed by
[25] J.C. Gálvez-Ruiz, E. Solano-Ruiz, S.A. Sánchez-Ruiz, R. Contreras, A. Flores-
Parra, Arkivoc (2008) 81.