Patent US3321491A successfully refreshed from Google Patents.
US3321491A
Expired / Lapsed
US
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Photochromic benzofuran compounds
Assignee: Wyeth Holdings LLC
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Filing: 1964-12-14
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Granted: 1967-05-23
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Expires: 1984-12-14
Abstract
No abstract record available.
Inventors
- 👤 Huffman Kenneth Robert
- 👤 Ullman Edwin Fisher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 20:32
CPC Classifications
C; C07; C07D; C07D307/00; C07D307/77; C07D307/91; C07D219/00; C07D219/04; C07D219/06; C07D307/78; C07D307/79; C07D307/80; C07D311/00; C07D311/02; C07D311/04; C07D311/22; C07D311/78; C07D311/80; C07D311/82; C07D311/84; C07D311/86; C07D333/00; C07D333/50; C07D333/52; C07D333/54; C07D333/56; C07D333/76; C07D493/00; C07D493/02; C07D493/08; G; G03; G03C; G03C1/00; G03C1/72; G03C1/73
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
6 words
PHOTOCHROMIC BENZOFURAN COMPOUNDS OF THE FORMULA
Claim 2
Dependent Claim
6 words
PHOTOCHROMIC BENZOFURAN COMPOUNDS OF THE FORMULA
References Cited (Backward Citations)
BE553621A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1970-05-22 | 1970-11-21 | 1971-05-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1974-05-22 | 1974-11-21 | 1975-05-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1978-05-22 | 1978-11-21 | 1979-05-23 | $7700.00 | Window Closed / Lapsed |