Which isomer is it, 1,2,5,6- or 1,4,5,8-tetrasubstituted cycloocta-1,3,5,7-tetraene? Synthesis of symmetrically tetrasubstituted cycloocta-1,3,5,7-tetraene derivatives
Gadigennavar, Savita; Ranganathan, Madhav; Sankararaman, Sethuraman; Organic & Biomolecular Chemistry 18 (2020) 9284–9291; doi:10.1039/D0OB01871F

data_7157791
_publ_section_title
;
 Which isomer is it, 1,2,5,6- or 1,4,5,8-tetrasubstituted
 cycloocta-1,3,5,7-tetraene? Synthesis of symmetrically tetrasubstituted
 cycloocta-1,3,5,7-tetraene derivatives
;
_journal_issue                   45
_journal_name_full               'Organic &amp; Biomolecular Chemistry'
_journal_page_first              9284
_journal_page_last               9291
_journal_paper_doi               10.1039/D0OB01871F
_journal_volume                  18
_journal_year                    2020
_chemical_absolute_configuration R
_chemical_formula_sum            'C28 H30 N2'
_chemical_formula_weight         394.54
_space_group_crystal_system      orthorhombic
_space_group_IT_number           19
_space_group_name_Hall           'P 2ac 2ab'
_space_group_name_H-M_alt        'P 21 21 21'
_atom_sites_solution_hydrogens   geom
_audit_creation_method           SHELXL-2014/7
_audit_update_record
;
2020-08-15 deposited with the CCDC.	2020-10-22 downloaded from the CCDC.
;
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   6.8590(5)
_cell_length_b                   17.0662(11)
_cell_length_c                   19.6709(10)
_cell_measurement_reflns_used    1637
_cell_measurement_temperature    296(2)
_cell_measurement_theta_max      20.27
_cell_measurement_theta_min      2.39
_cell_volume                     2302.6(3)
_computing_cell_refinement       'Bruker SAINT'
_computing_data_collection       'Bruker APEX2'
_computing_data_reduction        'Bruker SAINT'
_computing_molecular_graphics    'Bruker SHELXTL'
_computing_publication_material  'Bruker SHELXTL'
_computing_structure_refinement  'SHELXL-2014/7 (Sheldrick, 2014)'
_computing_structure_solution    'SHELXS-97 (Sheldrick 2008)'
_diffrn_ambient_temperature      296(2)
_diffrn_measured_fraction_theta_full 1.000
_diffrn_measured_fraction_theta_max 1.000
_diffrn_measurement_device_type  'Bruker APEX-II CCD'
_diffrn_measurement_method       '\f and \w scans'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0384
_diffrn_reflns_av_unetI/netI     0.0638
_diffrn_reflns_Laue_measured_fraction_full 1.000
_diffrn_reflns_Laue_measured_fraction_max 1.000
_diffrn_reflns_limit_h_max       4
_diffrn_reflns_limit_h_min       -8
_diffrn_reflns_limit_k_max       15
_diffrn_reflns_limit_k_min       -20
_diffrn_reflns_limit_l_max       21
_diffrn_reflns_limit_l_min       -23
_diffrn_reflns_number            9856
_diffrn_reflns_point_group_measured_fraction_full 0.999
_diffrn_reflns_point_group_measured_fraction_max 0.999
_diffrn_reflns_theta_full        24.994
_diffrn_reflns_theta_max         24.994
_diffrn_reflns_theta_min         1.580
_exptl_absorpt_coefficient_mu    0.066
_exptl_absorpt_correction_T_max  0.993
_exptl_absorpt_correction_T_min  0.984
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   'SADABS V2014/5(Bruker AXS.Inc)'
_exptl_crystal_colour            yellow
_exptl_crystal_density_diffrn    1.138
_exptl_crystal_description       Block
_exptl_crystal_F_000             848
_exptl_crystal_size_max          0.250
_exptl_crystal_size_mid          0.220
_exptl_crystal_size_min          0.100
_refine_diff_density_max         0.115
_refine_diff_density_min         -0.153
_refine_diff_density_rms         0.031
_refine_ls_abs_structure_details
; 
 Flack x determined using 802 quotients [(I+)-(I-)]/[(I+)+(I-)] 
 (Parsons, Flack and Wagner, Acta Cryst. B69 (2013) 249-259). 
;
_refine_ls_abs_structure_Flack   -0.8(10)
_refine_ls_extinction_coef       0.017(2)
_refine_ls_extinction_expression Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^
_refine_ls_extinction_method     'SHELXL-2014/7 (Sheldrick 2014'
_refine_ls_goodness_of_fit_ref   0.979
_refine_ls_hydrogen_treatment    constr
_refine_ls_matrix_type           full
_refine_ls_number_parameters     274
_refine_ls_number_reflns         4034
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      0.979
_refine_ls_R_factor_all          0.0893
_refine_ls_R_factor_gt           0.0459
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w=1/[\s^2^(Fo^2^)+(0.0503P)^2^] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0917
_refine_ls_wR_factor_ref         0.1133
_reflns_Friedel_coverage         0.730
_reflns_Friedel_fraction_full    0.997
_reflns_Friedel_fraction_max     0.997
_reflns_number_gt                2584
_reflns_number_total             4034
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            d0ob01871f2.cif
_cod_data_source_block           323
_cod_database_code               7157791
_shelx_shelxl_version_number     2014/7
_shelx_estimated_absorpt_t_min   0.984
_shelx_estimated_absorpt_t_max   0.993
_shelx_res_checksum              12038