No acid required: 4π and 6π electrocyclization reactions of dienyl diketones for the synthesis of cyclopentenones and 2H-Pyrans.
Jacob, Steven D.; Brooks, Joshua L.; Frontier, Alison J.; The Journal of organic chemistry 79 (2014) 10296–10302; doi:10.1021/jo501914w

data_4037610
_publ_section_title
;
 No acid required: 4\p and 6\p electrocyclization reactions of dienyl
 diketones for the synthesis of cyclopentenones and 2H-Pyrans.
;
_journal_issue                   21
_journal_name_full               'The Journal of organic chemistry'
_journal_page_first              10296
_journal_page_last               10302
_journal_paper_doi               10.1021/jo501914w
_journal_volume                  79
_journal_year                    2014
_chemical_formula_moiety         'C23 H25 N O2'
_chemical_formula_sum            'C23 H25 N O2'
_chemical_formula_weight         347.44
_chemical_name_common            frosj01
_space_group_crystal_system      orthorhombic
_space_group_IT_number           43
_space_group_name_Hall           'F 2 -2d'
_space_group_name_H-M_alt        'F d d 2'
_atom_sites_solution_hydrogens   mixed
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL-2014
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_formula_units_Z            16
_cell_length_a                   20.428(3)
_cell_length_b                   40.293(5)
_cell_length_c                   9.1395(11)
_cell_measurement_reflns_used    4094
_cell_measurement_temperature    100.0(5)
_cell_measurement_theta_max      33.01
_cell_measurement_theta_min      2.24
_cell_volume                     7522.8(17)
_computing_cell_refinement       'SAINT (Bruker, 2013)'
_computing_data_collection       'APEX2 (Bruker, 2013)'
_computing_data_reduction        'SAINT (Bruker, 2013)'
_computing_molecular_graphics    'SHELXTL (Sheldrick, 2008)'
_computing_publication_material  'SHELXTL (Sheldrick, 2008)'
_computing_structure_refinement  'SHELXL-2014 (Sheldrick, 2014)'
_computing_structure_solution    'SIR2011 (Burla et al., 2012)'
_diffrn_ambient_temperature      100.0(5)
_diffrn_measured_fraction_theta_full 0.998
_diffrn_measured_fraction_theta_max 0.969
_diffrn_measurement_device_type  'Bruker SMART APEX II CCD platform'
_diffrn_measurement_method       '\w scans'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0762
_diffrn_reflns_av_unetI/netI     0.1249
_diffrn_reflns_Laue_measured_fraction_full 0.998
_diffrn_reflns_Laue_measured_fraction_max 0.969
_diffrn_reflns_limit_h_max       21
_diffrn_reflns_limit_h_min       -35
_diffrn_reflns_limit_k_max       70
_diffrn_reflns_limit_k_min       -54
_diffrn_reflns_limit_l_max       11
_diffrn_reflns_limit_l_min       -15
_diffrn_reflns_number            20566
_diffrn_reflns_point_group_measured_fraction_full 0.796
_diffrn_reflns_point_group_measured_fraction_max 0.767
_diffrn_reflns_theta_full        37.785
_diffrn_reflns_theta_max         38.725
_diffrn_reflns_theta_min         2.022
_diffrn_source                   'fine-focus sealed tube'
_exptl_absorpt_coefficient_mu    0.078
_exptl_absorpt_correction_T_max  0.7477
_exptl_absorpt_correction_T_min  0.6098
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   'SADABS (Sheldrick, 2012)'
_exptl_crystal_colour            colorless
_exptl_crystal_density_diffrn    1.227
_exptl_crystal_description       block
_exptl_crystal_F_000             2976
_exptl_crystal_size_max          0.16
_exptl_crystal_size_mid          0.16
_exptl_crystal_size_min          0.14
_refine_diff_density_max         0.386
_refine_diff_density_min         -0.232
_refine_diff_density_rms         0.054
_refine_ls_abs_structure_details
; 
 Flack x determined using 1088 quotients [(I+)-(I-)]/[(I+)+(I-)] 
 (Parsons, Flack and Wagner, Acta Cryst. B69 (2013) 249-259). 
;
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   0.838
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     240
_refine_ls_number_reflns         8234
_refine_ls_number_restraints     1
_refine_ls_restrained_S_all      0.838
_refine_ls_R_factor_all          0.1072
_refine_ls_R_factor_gt           0.0544
_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^)+(0.0353P)^2^] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0904
_refine_ls_wR_factor_ref         0.1041
_reflns_Friedel_coverage         0.513
_reflns_Friedel_fraction_full    0.574
_reflns_Friedel_fraction_max     0.546
_reflns_number_gt                4596
_reflns_number_total             8234
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            jo501914w_si_002.cif
_cod_data_source_block           frosj01
_cod_original_cell_volume        7522.6(16)
_cod_database_code               4037610
_shelx_estimated_absorpt_t_min   0.988
_shelx_estimated_absorpt_t_max   0.989
_shelxl_version_number           2014-1
_shelx_res_checksum              7956
_shelx_hkl_checksum              1640