Metal-Free Brønsted Acid-Catalyzed Rearrangement of δ-Hydroxyalkynones to 2,3-Dihydro-4 H-pyran-4-ones: Total Synthesis of Obolactone and a Catechol Pyran Isolated from Plectranthus sylvestris.
Gholap, Sachin P.; Jangid, Dashrath; Fernandes, Rodney A.; The Journal of organic chemistry 84 (2019) 3537–3551; doi:10.1021/acs.joc.8b03141

data_4033933
_publ_section_title
;
 Metal-Free Br\/onsted Acid-Catalyzed Rearrangement of \d-Hydroxyalkynones
 to 2,3-Dihydro-4 H-pyran-4-ones: Total Synthesis of Obolactone and a
 Catechol Pyran Isolated from Plectranthus sylvestris.
;
_journal_issue                   6
_journal_name_full               'The Journal of organic chemistry'
_journal_page_first              3537
_journal_page_last               3551
_journal_paper_doi               10.1021/acs.joc.8b03141
_journal_volume                  84
_journal_year                    2019
_chemical_formula_moiety         'C11 H8 Br2 O2'
_chemical_formula_sum            'C11 H8 Br2 O2'
_chemical_formula_weight         331.99
_space_group_crystal_system      monoclinic
_space_group_IT_number           14
_space_group_name_Hall           '-P 2ybc'
_space_group_name_H-M_alt        'P 1 21/c 1'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     dual
_audit_creation_date             2018-11-14
_audit_creation_method
;
Olex2 1.2-ac4
(compiled 2018.05.17 svn.r3504 for Rigaku Oxford Diffraction, GUI svn.r5492)
;
_cell_angle_alpha                90
_cell_angle_beta                 92.023(4)
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   10.6794(5)
_cell_length_b                   7.5795(3)
_cell_length_c                   13.4516(6)
_cell_measurement_reflns_used    3543
_cell_measurement_temperature    150
_cell_measurement_theta_max      31.1040
_cell_measurement_theta_min      2.4670
_cell_volume                     1088.15(8)
_computing_cell_refinement       'CrystalClear-SM Expert 2.0 r7 (Rigaku, 2011)'
_computing_data_collection       'CrystalClear-SM Expert 2.0 r7 (Rigaku, 2011)'
_computing_data_reduction        'CrystalClear-SM Expert 2.0 r7 (Rigaku, 2011)'
_computing_molecular_graphics    'Olex2 (Dolomanov et al., 2009)'
_computing_publication_material  'Olex2 (Dolomanov et al., 2009)'
_computing_structure_refinement  'ShelXL (Sheldrick, 2015)'
_computing_structure_solution    'ShelXT (Sheldrick, 2015)'
_diffrn_ambient_temperature      150
_diffrn_detector                 CCD
_diffrn_detector_area_resol_mean 28.5714
_diffrn_detector_type            'Rigaku Saturn724+'
_diffrn_measured_fraction_theta_full 0.965
_diffrn_measured_fraction_theta_max 0.965
_diffrn_measurement_details
;
List of Runs (angles in degrees, time in seconds):

  # Type    Start    End  Width  t~exp~   \w     \q     \k     \f   Frames
--------------------------------------------------------------------------
  1  \w   -110.00  44.00   0.50    8.00    --  -20.00   0.00-108.00  308
  2  \w    -49.00 -31.00   0.50    8.00    --  -20.00 -72.00-180.00   36
;
_diffrn_measurement_device       'AFC12 (Right): Kappa 3 circle'
_diffrn_measurement_device_type  'Rigaku Saturn724+ (2x2 bin mode)'
_diffrn_measurement_method       'profile data from \w-scans'
_diffrn_measurement_specimen_support 'Mitegen 50um'
_diffrn_orient_matrix_type
'CrysAlisPro convention (1999,Acta A55,543-557)'
_diffrn_orient_matrix_UB_11      -0.0260894000
_diffrn_orient_matrix_UB_12      -0.0846928000
_diffrn_orient_matrix_UB_13      0.0079141000
_diffrn_orient_matrix_UB_21      -0.0201202000
_diffrn_orient_matrix_UB_22      -0.0038776000
_diffrn_orient_matrix_UB_23      -0.0507864000
_diffrn_orient_matrix_UB_31      0.0576938000
_diffrn_orient_matrix_UB_32      -0.0396139000
_diffrn_orient_matrix_UB_33      -0.0119911000
_diffrn_radiation_collimation    0.3
_diffrn_radiation_monochromator  Confocal
_diffrn_radiation_probe          x-ray
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0348
_diffrn_reflns_av_unetI/netI     0.0333
_diffrn_reflns_Laue_measured_fraction_full 0.965
_diffrn_reflns_Laue_measured_fraction_max 0.965
_diffrn_reflns_limit_h_max       12
_diffrn_reflns_limit_h_min       -12
_diffrn_reflns_limit_k_max       9
_diffrn_reflns_limit_k_min       -6
_diffrn_reflns_limit_l_max       11
_diffrn_reflns_limit_l_min       -15
_diffrn_reflns_number            3284
_diffrn_reflns_point_group_measured_fraction_full 0.965
_diffrn_reflns_point_group_measured_fraction_max 0.965
_diffrn_reflns_theta_full        24.991
_diffrn_reflns_theta_max         24.991
_diffrn_reflns_theta_min         3.031
_diffrn_source                   'Rotating Anode'
_diffrn_source_current           24.0
_diffrn_source_power             1.2
_diffrn_source_target            Mo
_diffrn_source_type              'Rotating Anode'
_diffrn_source_voltage           50.0
_exptl_absorpt_coefficient_mu    7.424
_exptl_absorpt_correction_T_max  1.00000
_exptl_absorpt_correction_T_min  0.33297
_exptl_absorpt_correction_type   numerical
_exptl_absorpt_process_details
;
CrysAlisPro 1.171.39.46 (Rigaku Oxford Diffraction, 2018)
Empirical absorption correction using spherical harmonics,
 implemented in SCALE3 ABSPACK scaling algorithm.
;
_exptl_crystal_colour            colourless
_exptl_crystal_colour_primary    colourless
_exptl_crystal_density_diffrn    2.026
_exptl_crystal_description       plate
_exptl_crystal_F_000             640
_exptl_crystal_size_max          0.159
_exptl_crystal_size_mid          0.125
_exptl_crystal_size_min          0.095
_refine_diff_density_max         0.417
_refine_diff_density_min         -0.481
_refine_diff_density_rms         0.112
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.046
_refine_ls_hydrogen_treatment    constr
_refine_ls_matrix_type           full
_refine_ls_number_parameters     136
_refine_ls_number_reflns         1836
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.046
_refine_ls_R_factor_all          0.0295
_refine_ls_R_factor_gt           0.0250
_refine_ls_shift/su_max          0.001
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w=1/[\s^2^(Fo^2^)+(0.0436P)^2^+0.3794P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0667
_refine_ls_wR_factor_ref         0.0681
_reflns_Friedel_coverage         0.000
_reflns_number_gt                1720
_reflns_number_total             1836
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            jo8b03141_si_004.cif
_cod_data_source_block           raf-spg-1264_mo
_cod_original_cell_volume        1088.16(8)
_cod_database_code               4033933
_shelx_shelxl_version_number     2014/7
_shelx_estimated_absorpt_t_max   0.539
_shelx_estimated_absorpt_t_min   0.385
_reflns_odcompleteness_completeness 82.22
_reflns_odcompleteness_iscentric 1
_reflns_odcompleteness_theta     30.94
_olex2_refinement_description
;
1. Fixed Uiso
 At 1.2 times of:
  All C(H) groups, All C(H,H) groups
2.a Secondary CH2 refined with riding coordinates:
 C4(H4A,H4B), C3(H3A,H3B)
2.b Aromatic/amide H refined with riding coordinates:
 C11(H11), C10(H10), C9(H9), C8(H8)
;
_shelx_res_checksum              29460
_shelx_hkl_checksum              14581
_olex2_submission_special_instructions 'No special instructions were received'
_oxdiff_exptl_absorpt_empirical_details
;
Empirical correction (ABSPACK) includes:
- Absorption correction using spherical harmonics
- Frame scaling
- Detector area scaling
;
_oxdiff_exptl_absorpt_empirical_full_max 1.729
_oxdiff_exptl_absorpt_empirical_full_min 0.620