穴田 仁洋

A phenanthridine synthesis based on an alkoxy-group-elimination-type S _N Ar reaction, a largely unexplored transformation in S _N Ar chemistry, was achieved.

Abstract A divergent synthetic route to indanes and benzoxepines is reported. The key to the divergence is the selection of the catalytic system. Whereas treating benzylidene malonate with a 1-alkoxyalkyl group at the ortho position with Sc(OTf)3 gave indanes via an internal redox reaction ([1,4]-hydride shift/cyclization), the simultaneous use of Sc(OTf)3 and PhCO2H afforded benzoxepines through an intramolecular nucleophilic substitution reaction.

The first continuous‐flow intramolecular dehydrative Friedel–Crafts alkylation of 1‐substituted ω‐arylalkan‐1‐ols is successfully achieved. The reaction is completed by a single pass of a solution of substrates in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) at 25 °C through a cartridge packed with hydroxy‐substituted sulfonic acid‐functionalized silica gel (HO‐SAS) as a water‐tolerant immobilized Brønsted acid catalyst with a residence time of only 40–80 s. The efficiency of the concise catalytic process is demonstrated by the short‐step synthesis of the bisnorlignan natural product pachypostaudin A.

The total synthesis of breviscapin B, a norlignan natural product having an unusual 2,2-diaryltetrahydrofuran skeleton, has been achieved via intramolecular dehydrative Williamson ether synthesis as a key step.

A concise and direct cyanation of secondary and tertiary benzylic and allylic alcohols catalyzed by Brønsted acid has been developed using trimethylsilyl cyanide (TMSCN) as a cyanide source and 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) as a solvent. The present transition metal‐free catalytic process is operationally simple to perform under “open‐flask” conditions and it is applicable to the preparation of a number of α‐arylacetonitriles as well as late‐stage material transformations. The effectiveness of the present protocol was further demonstrated by the first enantioselective synthesis and determination of the absolute configuration of verimol F.

Divergent synthesis of multi-substituted phenanthrenes based on an internal redox reaction/ring expansion sequence was achieved.

Abstract A Brønsted acid‐catalyzed, transition metal‐free intramolecular 7‐endo hydroarylation reaction of 1,5‐diaryl‐1‐pentynes has been developed. The use of 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) as a solvent was found to be critical for this process. Using the present methodology, we have accomplished the synthesis of KGP‐18, an analogue of the anticancer natural product combretastatin A4. magnified image