A new approach to construct a fused 2-ylidene chromene ring: highly regioselective synthesis of novel chromeno quinoxalines.
Shiva Kumar, K.; Rambabu, D.; Prasad, Bagineni; Mujahid, Mohammad; Krishna, G. Rama; Basaveswara Rao, M. V.; Malla Reddy, C.; Vanaja, G. R.; Kalle, Arunasree M.; Pal, Manojit; Organic & biomolecular chemistry 10 (2012) 4774–4781; doi:10.1039/c2ob25416f

data_7152386
_publ_section_title
;
 A new approach to construct a fused 2-ylidene chromene ring: highly
 regioselective synthesis of novel chromeno quinoxalines.
;
_journal_issue                   24
_journal_name_full               'Organic &amp; biomolecular chemistry'
_journal_page_first              4774
_journal_page_last               4781
_journal_paper_doi               10.1039/c2ob25416f
_journal_volume                  10
_journal_year                    2012
_chemical_formula_sum            'C21 H20 N2 O2'
_chemical_formula_weight         332.15
_space_group_IT_number           14
_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                 106.361(3)
_cell_angle_gamma                90.00
_cell_formula_units_Z            4
_cell_length_a                   19.497(2)
_cell_length_b                   5.5899(7)
_cell_length_c                   16.139(2)
_cell_measurement_temperature    273(2)
_cell_volume                     1687.7(3)
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 2008)'
_computing_structure_solution    'SHELXS-97 (Sheldrick, 2008)'
_diffrn_ambient_temperature      273(2)
_diffrn_measured_fraction_theta_full 1.000
_diffrn_measured_fraction_theta_max 1.000
_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  0.0401
_diffrn_reflns_av_sigmaI/netI    0.0366
_diffrn_reflns_limit_h_max       25
_diffrn_reflns_limit_h_min       -25
_diffrn_reflns_limit_k_max       7
_diffrn_reflns_limit_k_min       -7
_diffrn_reflns_limit_l_max       21
_diffrn_reflns_limit_l_min       -21
_diffrn_reflns_number            17443
_diffrn_reflns_theta_full        28.00
_diffrn_reflns_theta_max         28.00
_diffrn_reflns_theta_min         1.09
_exptl_absorpt_coefficient_mu    0.085
_exptl_crystal_density_diffrn    1.316
_exptl_crystal_density_method    'not measured'
_exptl_crystal_F_000             712
_refine_diff_density_max         0.569
_refine_diff_density_min         -0.311
_refine_diff_density_rms         0.093
_refine_ls_extinction_coef       0.0051(17)
_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   1.042
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     232
_refine_ls_number_reflns         4075
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.042
_refine_ls_R_factor_all          0.0936
_refine_ls_R_factor_gt           0.0579
_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^)+(0.0975P)^2^+1.0814P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1549
_refine_ls_wR_factor_ref         0.1905
_reflns_number_gt                2670
_reflns_number_total             4075
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            c2ob25416f.txt
_cod_data_source_block           drb_11_a
_cod_original_cell_volume        1687.6(4)
_cod_database_code               7152386