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_4033937
_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         'C12 H10 O4'
_chemical_formula_sum            'C12 H10 O4'
_chemical_formula_weight         218.20
_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             2018-10-21
_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                 97.111(6)
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   5.4376(3)
_cell_length_b                   9.2746(5)
_cell_length_c                   19.1403(12)
_cell_measurement_reflns_used    3625
_cell_measurement_temperature    150
_cell_measurement_theta_max      30.9360
_cell_measurement_theta_min      2.4190
_cell_volume                     957.85(10)
_computing_cell_refinement       'CrysAlisPro 1.171.38.43 (Rigaku OD, 2015)'
_computing_data_collection       'CrysAlisPro 1.171.38.43 (Rigaku OD, 2015)'
_computing_data_reduction        'CrysAlisPro 1.171.38.43 (Rigaku OD, 2015)'
_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 plate'
_diffrn_detector_area_resol_mean 28.5714
_diffrn_detector_type            'Rigaku Saturn724+'
_diffrn_measured_fraction_theta_full 0.996
_diffrn_measured_fraction_theta_max 0.996
_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    -94.50  19.00   0.50    8.00    --  -20.00 -72.00-180.00  227
  2  \w    -71.00  -7.00   0.50    8.00    --  -20.00   0.00-180.00  128
  3  \w   -110.00   9.50   0.50    8.00    --  -20.00 -72.00 -36.00  239
  4  \w   -110.00 -89.00   0.50    8.00    --  -20.00 -72.00 108.00   42
;
_diffrn_measurement_device       'abstract diffractometer'
_diffrn_measurement_device_type
'dtrek-CrysAlisPro-abstract goniometer imported rigaku-d*trek images'
_diffrn_measurement_method       '\w scans'
_diffrn_measurement_specimen_support 'Mitegen 50um'
_diffrn_orient_matrix_type
'CrysAlisPro convention (1999,Acta A55,543-557)'
_diffrn_orient_matrix_UB_11      0.0264039000
_diffrn_orient_matrix_UB_12      -0.0505416000
_diffrn_orient_matrix_UB_13      0.0277061000
_diffrn_orient_matrix_UB_21      -0.0475899000
_diffrn_orient_matrix_UB_22      -0.0562815000
_diffrn_orient_matrix_UB_23      -0.0229280000
_diffrn_orient_matrix_UB_31      0.1196693000
_diffrn_orient_matrix_UB_32      -0.0111858000
_diffrn_orient_matrix_UB_33      -0.0100992000
_diffrn_radiation_collimation    0.3
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_probe          x-ray
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0417
_diffrn_reflns_av_unetI/netI     0.0459
_diffrn_reflns_Laue_measured_fraction_full 0.996
_diffrn_reflns_Laue_measured_fraction_max 0.996
_diffrn_reflns_limit_h_max       4
_diffrn_reflns_limit_h_min       -6
_diffrn_reflns_limit_k_max       11
_diffrn_reflns_limit_k_min       -11
_diffrn_reflns_limit_l_max       22
_diffrn_reflns_limit_l_min       -22
_diffrn_reflns_number            5543
_diffrn_reflns_point_group_measured_fraction_full 0.996
_diffrn_reflns_point_group_measured_fraction_max 0.996
_diffrn_reflns_theta_full        24.999
_diffrn_reflns_theta_max         24.999
_diffrn_reflns_theta_min         2.145
_diffrn_source                   'fine-focus sealed X-ray tube'
_diffrn_source_current           24.0
_diffrn_source_power             1.2
_diffrn_source_target            Mo
_diffrn_source_type              'Enhance (Mo) X-ray Source'
_diffrn_source_voltage           50.0
_exptl_absorpt_coefficient_mu    0.115
_exptl_absorpt_correction_T_max  1.00000
_exptl_absorpt_correction_T_min  0.52198
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details
;
CrysAlisPro 1.171.38.43 (Rigaku Oxford Diffraction, 2015)
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    1.513
_exptl_crystal_description       block
_exptl_crystal_F_000             456
_exptl_crystal_size_max          0.16
_exptl_crystal_size_mid          0.13
_exptl_crystal_size_min          0.11
_refine_diff_density_max         0.225
_refine_diff_density_min         -0.270
_refine_diff_density_rms         0.060
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.056
_refine_ls_hydrogen_treatment    constr
_refine_ls_matrix_type           full
_refine_ls_number_parameters     145
_refine_ls_number_reflns         1682
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.056
_refine_ls_R_factor_all          0.0502
_refine_ls_R_factor_gt           0.0379
_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^)+(0.0403P)^2^+0.3765P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0872
_refine_ls_wR_factor_ref         0.0967
_reflns_Friedel_coverage         0.000
_reflns_number_gt                1414
_reflns_number_total             1682
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            jo8b03141_si_002.cif
_cod_data_source_block           raf-spg-99-a_mo
_cod_database_code               4033937
_shelx_shelxl_version_number     2014/7
_shelx_estimated_absorpt_t_max   0.988
_shelx_estimated_absorpt_t_min   0.982
_reflns_odcompleteness_completeness 90.98
_reflns_odcompleteness_iscentric 1
_reflns_odcompleteness_theta     31.14
_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:
 C11(H11A,H11B), C1(H1A,H1B), C12(H12A,H12B)
2.b Aromatic/amide H refined with riding coordinates:
 C3(H3), C5(H5), C6(H6), C9(H9)
;
_shelx_res_checksum              21131
_shelx_hkl_checksum              37592
_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 1.654
_oxdiff_exptl_absorpt_empirical_full_min 0.678