Electron-deficient dienes. 5. An inverse-electron-demand Diels-Alder approach to 2-substituted 4-methoxyxanthones and 3,4-dimethoxyxanthones.
Dang, Anh-Thu; Miller, David O.; Dawe, Louise N.; Bodwell, Graham J.; Organic letters 10 (2008) 233–236; doi:10.1021/ol702614b

data_1504490
_publ_section_title
;
 Electron-deficient dienes. 5. An inverse-electron-demand Diels-Alder
 approach to 2-substituted 4-methoxyxanthones and 3,4-dimethoxyxanthones.
;
_journal_issue                   2
_journal_name_full               'Organic letters'
_journal_page_first              233
_journal_page_last               236
_journal_paper_doi               10.1021/ol702614b
_journal_volume                  10
_journal_year                    2008
_chemical_formula_sum            'C18 H18 O6'
_chemical_formula_weight         330.32
_space_group_IT_number           14
_symmetry_cell_setting           monoclinic
_symmetry_space_group_name_Hall  '-P 2ybc'
_symmetry_space_group_name_H-M   'P 1 21/c 1'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL-97
_cell_angle_alpha                90.00
_cell_angle_beta                 96.645(2)
_cell_angle_gamma                90.00
_cell_formula_units_Z            4
_cell_length_a                   8.4566(7)
_cell_length_b                   10.6306(9)
_cell_length_c                   17.7943(16)
_cell_measurement_reflns_used    6333
_cell_measurement_temperature    153(2)
_cell_measurement_theta_max      30.8
_cell_measurement_theta_min      1.9
_cell_volume                     1588.9(2)
_computing_cell_refinement       'CrystalClear (Rigaku/MSC Inc., 2005)'
_computing_data_collection       'CrystalClear (Rigaku/MSC Inc., 2005)'
_computing_data_reduction        'CrystalClear (Rigaku/MSC Inc., 2005)'
_computing_molecular_graphics    'Crystalstructure (Rigaku/MSC Inc., 2005)'
_computing_publication_material  'Crystalstructure (Rigaku/MSC Inc., 2005)'
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 1997)'
_computing_structure_solution    'SHELXS-97 (Sheldrick, 1990)'
_diffrn_ambient_temperature      153(2)
_diffrn_detector_area_resol_mean 14.63
_diffrn_measured_fraction_theta_full 0.998
_diffrn_measured_fraction_theta_max 0.998
_diffrn_measurement_device_type  'Rigaku Saturn'
_diffrn_measurement_method       \w
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_source         'fine-focus sealed tube'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71070
_diffrn_reflns_av_R_equivalents  0.0150
_diffrn_reflns_av_sigmaI/netI    0.0131
_diffrn_reflns_limit_h_max       10
_diffrn_reflns_limit_h_min       -10
_diffrn_reflns_limit_k_max       13
_diffrn_reflns_limit_k_min       -13
_diffrn_reflns_limit_l_max       11
_diffrn_reflns_limit_l_min       -23
_diffrn_reflns_number            14537
_diffrn_reflns_theta_full        27.50
_diffrn_reflns_theta_max         27.50
_diffrn_reflns_theta_min         2.30
_exptl_absorpt_coefficient_mu    0.104
_exptl_absorpt_correction_T_max  0.9827
_exptl_absorpt_correction_T_min  0.9704
_exptl_absorpt_correction_type   numerical
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.381
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       prism
_exptl_crystal_F_000             696
_exptl_crystal_size_max          0.38
_exptl_crystal_size_mid          0.38
_exptl_crystal_size_min          0.35
_refine_diff_density_max         0.293
_refine_diff_density_min         -0.211
_refine_diff_density_rms         0.044
_refine_ls_extinction_coef       0.013(3)
_refine_ls_extinction_expression Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^
_refine_ls_extinction_method     SHELXL
_refine_ls_goodness_of_fit_ref   1.064
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     219
_refine_ls_number_reflns         3628
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.064
_refine_ls_R_factor_all          0.0435
_refine_ls_R_factor_gt           0.0427
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0626P)^2^+0.4961P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1134
_refine_ls_wR_factor_ref         0.1143
_reflns_number_gt                3545
_reflns_number_total             3628
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            ol702614b-file001.cif
_cod_data_source_block           shelxl
_cod_database_code               1504490