A Facile Phenol-Driven Intramolecular Diastereoselective Thermal/Base-Catalyzed Dipolar [2 + 2] Annulation Reactions: An Easy Access to Complex Bioactive Natural and Unnatural Benzopyran Congeners
Mukulesh Mondal; Vedavati G. Puranik; Narshinha P. Argade; Journal of Organic Chemistry 72 (2007) 2068–2076; doi:10.1021/jo0624344

data_4022779
_publ_section_title
;
 A Facile Phenol-Driven Intramolecular Diastereoselective
 Thermal/Base-Catalyzed Dipolar [2 + 2] Annulation Reactions: An Easy
 Access to Complex Bioactive Natural and Unnatural Benzopyran Congeners
;
_journal_name_full               'Journal of Organic Chemistry'
_journal_page_first              2068
_journal_page_last               2076
_journal_paper_doi               10.1021/jo0624344
_journal_volume                  72
_journal_year                    2007
_chemical_formula_moiety         'C18 H20 O4'
_chemical_formula_sum            'C18 H20 O4'
_chemical_formula_weight         300.34
_chemical_melting_point          530.1(10)
_chemical_name_common            Cyclobutaindene
_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                 93.676(2)
_cell_angle_gamma                90.00
_cell_formula_units_Z            4
_cell_length_a                   13.3486(15)
_cell_length_b                   7.9630(9)
_cell_length_c                   13.8757(15)
_cell_measurement_reflns_used    1024
_cell_measurement_temperature    297(2)
_cell_measurement_theta_max      21.361
_cell_measurement_theta_min      2.643
_cell_volume                     1471.9(3)
_computing_cell_refinement       'BRUKER SAINT'
_computing_data_collection       'BRUKER SMART'
_computing_data_reduction        'BRUKER SAINT'
_computing_molecular_graphics    'SHELXTL and PLATON'
_computing_publication_material  SHELXTL
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 1997)'
_computing_structure_solution    'SHELXS-97 (Sheldrick, 1990)'
_diffrn_ambient_temperature      297(2)
_diffrn_measured_fraction_theta_full 0.999
_diffrn_measured_fraction_theta_max 0.999
_diffrn_measurement_device       ' Bruker Smart APEX'
_diffrn_measurement_device_type  ' CCD Area Detector'
_diffrn_measurement_method       'Omega Scan'
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_source         'fine-focus sealed tube'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0596
_diffrn_reflns_av_sigmaI/netI    0.0605
_diffrn_reflns_limit_h_max       13
_diffrn_reflns_limit_h_min       -15
_diffrn_reflns_limit_k_max       9
_diffrn_reflns_limit_k_min       -9
_diffrn_reflns_limit_l_max       16
_diffrn_reflns_limit_l_min       -16
_diffrn_reflns_number            9215
_diffrn_reflns_theta_full        25.00
_diffrn_reflns_theta_max         25.00
_diffrn_reflns_theta_min         1.53
_exptl_absorpt_coefficient_mu    0.095
_exptl_absorpt_correction_T_max  0.9945
_exptl_absorpt_correction_T_min  0.9752
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   'Omega Scan'
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.355
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       rectangular
_exptl_crystal_F_000             640
_exptl_crystal_size_max          0.27
_exptl_crystal_size_mid          0.17
_exptl_crystal_size_min          0.06
_refine_diff_density_max         0.190
_refine_diff_density_min         -0.153
_refine_diff_density_rms         0.040
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.010
_refine_ls_hydrogen_treatment    constr
_refine_ls_matrix_type           full
_refine_ls_number_parameters     203
_refine_ls_number_reflns         2594
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.010
_refine_ls_R_factor_all          0.1036
_refine_ls_R_factor_gt           0.0501
_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^)+(0.0585P)^2^+0.0176P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1043
_refine_ls_wR_factor_ref         0.1259
_reflns_number_gt                1513
_reflns_number_total             2594
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            jo0624344si20061229_083042.cif
_cod_data_source_block           OxacyclobutaindeneCompound_4a
_cod_depositor_comments
;
The following automatic conversions were performed:
'_symmetry_cell_setting' value 'Monoclinic' changed to 'monoclinic'
according to '/home/saulius/struct/CIF-dictionaries/cif_core.dic'
dictionary named 'cif_core.dic' version 2.4.1 from 2010-06-29.

Automatic conversion script
Id: cif_fix_enum 1527 2010-12-29 10:47:43Z saulius 

The following automatic conversions were performed:

'_chemical_melting_point' value '256-258 degree Centigrade' was
changed to '530.1(10)' - it was converted from degrees Celsius(C) to
Kelvins(K), the average value was taken and precision was estimated.

Automatic conversion script
Id: cif_fix_values 1646 2011-03-28 12:23:43Z adriana 
;
_cod_original_sg_symbol_H-M      'P 21/c'
_cod_database_code               4022779